Wow. I feel your pain. Such a disaster is hard on any gardener, but especially discouraging to a newbie. Your excellent video allows me to confirm your diagnosis of powdery mildew running rampant thru your garden, squash bug eggs & nymphs on leaves, and bacterial wilt spread by the cucumber beetles... Knowing your enemy is at least half the battle!

Do not give in to despair and do not give up! The Gardener's Mantra is "There's always next year!" Meantime, visit your local farmers' markets to get the veggies your garden has failed to provide.

Let me point out, before offering suggestions for next year's garden, that it would be helpful when you ask any garden question here to say what zone you are in since there are five (!) different zones in PA (I lived some years W of Philly, then E of Pittsburgh). If you are unsure, see http://www.growit.com/bin/USDAZoneMaps.exe?MyState=pa
(You could add the zone and general geographic area or city by your GW username, as I have done.)

Powdery mildew: the spores are everywhere, and the fungus proliferates during cool, moist nighttime conditions (which is why one should never water the lawn or garden after about 3:00 PM--give the leaves a chance to dry off before dark,--and always try to water the base of plants, not the foliage, at any time). A really healthy plant usually can withstand this at least for some time before succumbing. Always, when ordering seeds, it is wise to look for cultivars/varieties that are resistant to various diseases and purchase those. There also are organic fungicides that will prevent or control such diseases as black spot, powdery mildew, various blights, etc. Gardens Alive (with which I have no connection aside from that of customer) has a lot of good products, but so have other companies. Shop around on line as the advertising dollars of these product manufacturers are no match for the big chemical companies and so you won't find much yet in the big stores. Still, there are lots more organic products available locally than there were previously. (Not much at all when I began gardening organically over 40 years ago.)

Your melons that are rotted on the end are a prime example of blossom end rot; on cucurbits generally due to alternating extremes of moisture -- water/drought. (Rather than me re-inventing the wheel & taking up extra space here, please look up terms you may not understand, like blossom end rot, in Gardenweb's glossary or other online source.) For now, pick off and compost affected fruits; they are simply using nutrients your plant could better spend elsewhere. Read on to learn of possible solution for the future.

And yes--you are right again in noting that cucumber beetles are the vector for bacterial wilt--about which I am sorry to tell you NOTHING may be done once it has set in. Your vines are goners. But there are solutions; read on!

But do not start spraying any chemical pesticides--or if you have, stop it!!! These kill honeybees as well as natural predators like tachnid flies, soldier beetles, parasitic nematodes, braconid wasps, lacewings, ladybugs, and others that will help in the battle against pest species. There are such things as bioinsecticides if you must spray, but read on...

From what I see of your soil, you need LOTS more organic matter--compost, compost, compost! This would make for healthier plants that then would be more resistant to and be able to ward off attacks from pest insects and disease. In addition to adding nutrients to the soil, organic matter acts like a sponge, allowing the soil to absorb water and hold it for release as plants need it. You cannot have too much organic matter in your soil. (My raised beds are filled entirely with pure compost I purchased by the trailer load from our local municipal yard waste facility. No "top soil.")

You need to use lots of MULCH. If you have home-made compost that is still not quite "finished," it makes an excellent mulch (use 1-2") to be added right after planting your seedlings or, if you direct-seeded, once the seeds are several inches high. After the soil has warmed up completely and the vines have just started to run, top that (the area under and around to either side of the plants at least 12h out) with lots of chopped leaves (saved from the previous autumn) or straw (NOT hay, which is full of weed seeds!), using 4-6" of that. This will provide 3 benefits: hold in soil moisture, keep weed seeds from germinating, and add more organic matter to the soil as it decays, and encourage the soil microorganisms and invertebrates. Take all the help you can get from Naturefs laborers!
Some people may recommend using black plastic as mulch. Don't. It adds nothing to the soil, the soil cannot "breathe" (actually, the soil microorganisms die), no more moisture can get to the root systems, it will photo degrade, making a mess in the garden, the toxic chemicals released as the plastic degrades do not belong in the garden...etc., etc.. (Have you caught on yet that I am advising ONLY organic methods?)

In addition to concentrating on building up soil fertility (and fall is an excellent time to amend soil (see GW's SOILS forum!) and the use of bioinsecticides, you also would have better luck with controlling insect pests by the early use of floating row cover (spun polyester fabric, widely available online and at larger nurseries; one brand is Reemay) over seedlings. Leave it on until female flowers appear (not just male flowers, which generally appear several days or more prior to the females) since bees will need to pollinate them. By then the plants should be strong enough to resist insects & disease to some extent. Also, again, read the descriptions of squash & cukes in the catalogs, looking for those that are parthenogenic (a ten-dollar botanist's term for plants that need not have a male partner to set fruit. ('Diva' is a cultivar I plant. Nice for slicing or pickling.) Except for a few minutes removal to pick your lovely cucumbers each day or so as they ripen you can leave the row cover on 24/7 to exclude beetles!

You asked: "Is there any disease going to be leftover in the soil? Is there something I can do to eliminate any disease left in the soil so it is gone for next year?"
The mildew spores are in the air, as I mentioned earlier; the spray I mentioned will help with that. The beetles spread bacterial wilt. The insects are what you want to get rid of. You should squash the squash bug eggs as soon as you see them. There also are organic products like cuke beetle traps and insecticidal oil sprays that smother insects & their eggs. Look for those on line, too. Most importantly, clean up all garden residues & compost it in a hot, active pile (easy to mak; check out the compost forum here or at any of several good composting websites) or else burn it to destroy over-wintering eggs or larvae.
From Cornell: "Cucumbers and cantaloupe are susceptible to bacterial wilt and should be treated within 24 hours if plants along the edges are heavily damaged or have 5 or more beetles per plant. Following the first treatment, apply follow-up treatments only if there is at least one beetle per plant."

Guess this is really long enough. Check with your Penn State cooperative extension office for more info. Sorry; once I get going I tend to ramble on. :-)
Hope I helped a bit, even if only with ideas for next year.

I do want to add that you did a great job on your trellises, and you did well to make slings for the growing melons. (Looks like maybe you have a good reference book, maybe Square Foot Gardening?). Also, putting boards under the ripening melons was good since they are not trellised.
I am curious, though: what's with the hardware cloth (woven wire) I see lying on the ground?
Best wishes, CK

Such a long reply and nothing about the cucumber beetle larvae?? You may have vine borers. You can remove them by cutting the vine length ways until you see them. Then with a pair of needle nose pliers, hemostats or tweezers reach in and pull them out. Your plants may not survive the surgery but it's worth trying because some do survive and can still bare fruit.