I had a Bosch that we bought in 2001 and when we moved it was my favorite thing to leave at our old house! It rarely cleaned dishes, left residue, often had standing water in bottom (yes I cleaned out the filter). And yet, when we were redoing our new kitchen I felt like everyone was pushing the Bosch. (I don't like he racking systems in the Miele as much as I have tried to during our 2 years of planning). Today was final decision today so I went to the local high end appliance store. When our salesman found I was not married to one brand, he said that his recent (over the past year) favorite was the KitchenAid Superba 60. It felt SO much sturdier than the Bosch, Miele or Asko. NOTE: If your counters are 24" deep and you want a panel ready model, these are the only three models that will ensure a "built-in" seamless look). He said some resist the high end KA because the want the "high end" DW brands, but he has fewer problems and more excellent reviews from the Kitchen Aid. The house we moved into has a 40 year old KA (yes, I know, they are made my entirely different companies, but still...) so we are going to give it a try. It has the three racks (my least favorite part of the Miele, but the rest of the racking system isn't as wacky), the silverware tray can be removed. The upper rack moves up and down so easily. He also mentioned that the KUD30 was the best "value" - had the most features and was still fairly quiet. We decided on the 60 because it was quieter and we are getting two (and expect that there will be many times when both are running at the same time) and it seemed to have an upgraded drying system and a sturdier rack system.

There is really no reason install a garbage disposal. The tail piece to connect the dishwasher to the drain is only a couple bucks. But, if you are going to someday install a garbage disposal, it's cheaper to have all the wiring and plumbing for both done at the same time.

A proper 120v circuit has a hot, neutral, and a ground. What you describe is a hot and a ground. While such an arrangement will function it's certainly not to code and potentially dangerous. As suggested your best bet is to run a new 20-amp circuit. The other alternative and I'm not sure if current code allows this is to remove the existing 50 amp, double pole breaker and replace it with a 20 amp, single pole breaker. Use one of the two insulated wires in the existing cable as your hot and the other as the neutral. The uninsulated wire is the ground. The problem is that the heavier wire typically won't fit in a 20 amp breaker or receptacle. So you need to connect a short length of 12 ga. wire at each end of the two heavy wires, most likely with a split bolt. I'm sure someone will comment on if such a method meets current code.

The better (less confusing) way to check a switch is to disconnect it and test it with an ohm meter between the common and each of the traveler terminals. If you have continuity between the common and one traveler terminal when the switch is in one position, and between the common and the other traveler terminal when the switch is in the other position, then the switch is good. With the mtvhike method, it could still just be wired wrong. (Inconclusive) As you can see, there is more than one way that only one or zero terminals could be hot if it is wired wrong. Or even that all 3 terminals are hot.