Otherwise it's a great looking lawn! You are still watering too much. I'm 500 miles south of you and got an inch of rain exactly 15 days ago. I watered two spots today for the first time since the rain. Most of the lawn still does not need water. At this time you should be backing off beyond the 7 days and looking at 10 or 15. With much cooler weather the soil does not dry out as quickly. Oh and the other thing you should be doing is putting down corn meal instead of asking so many questions. There is no substitute for getting it down NOW. Be sure to treat the entire lawn and not just the spots. You can't really tell how big the disease is affecting the soil. Plus the corn meal will really green up the spots you treat, so you'd go from brown to deep green.

My guess would be heat stress and bug damage. When a portion of lawn becomes stressed it starts to weaken and bugs take full advantage of those areas. Im sure most of the damage is already done, but pay close attention to the area to see if its spreading. For now you could apply some Quality Compost in and around the trouble spots @ 1/4 to 1/2" thick. Brush or lightly rake the compost off the grass blades and down closer to the existing soil. As for the grass blades wilting/curling: This is perfectly normal. The grass blades curl/reduce surface area during the heat of the day in order to conserve water from evaporation through their leafs. If by the following morning the grass blades are still wilted, the grass should be watered within 24hrs. Are you sure your apply 3/4 to 1" of water with each irrigation cycle? If not do the tuna can test(link below) Here is a link that might be useful: How to calibrate your sprinkler

I have a sloped back yard around my pool, which is much more steep than your slope in the pictures, covered in St. Augustine. I too detest lawns, but I have no money right now, so my St. Augustine is here to stay. I water my St. Augustine with an irrigation system on my allotted days and once yearly treat with weed/feed. Yes, my St. Aug is great on bare feet and very healthy looking. I have no problems with maintaining it on the slope. I'm not bragging, I'm just trying to explain that I have personal experience with this situation. I think your first problem is with the underlying sand. My underlying soil is a thick layer of decayed organic material, on top of a thin layer of sand, on top of a thick layer of loose clay. It's clear from your photos that the mower tires are disturbing the St. Aug's growth. That is very easy to do regardless of the underlying soil, but especially easy in sand such as you have. I think your second problem is with your lawn guy. Seriously. And, I mean absolutely no offense. Your lawn is covered in weeds. It didn't happen overnight, although sometimes it might seem that way. Your lawn guy should know (1) how to mow on a slope without destroying the roots, (2) how to point out a weed problem before it becomes a massive weed problem like you have. How convenient for him that you need sod replacement?!?! Isn't his job routine lawn care, not routine lawn destroying and replacement? That being said, I have a cheap temporary solution for you. I see in the first picture, to the left of the hose/brick path, you have a bush/tree surrounded by a small circle of mulch. And, in the second picture, you have another tree just down slope from the pool, surrounded by another small circle of mulch. I would take a sharp straight-edged shovel and cut away shovel sized squares of sod in a circular pattern around those trees. Making much, much larger circles around the trees. Take a section of the sandy/weedy area, cover thickly in newspaper, wet newspaper, then lay your homemade sod squares on top of the wet paper. Water daily until they take root and can survive on their own. Go back and extend the mulched area around the two trees, so your weed problem doesn't extend under the trees. This should really be done in stages, because the sod squares that you cut out and move need to be kept wet during the moving process. I say my solution is cheap, because you can buy mulch for $1.68 at the big box stores these days, and you would probably need 10 bags. Less than $20. Of course you will have a little extra water expense from having to water daily to establish the newly sodded sections. It is a little bit back breaking, but I'm sure you can either do it or find someone to help. I say my solution is temporary because, ideally, you could eventually plant some sort of hearty, Florida friendly ground cover over that entire area. In the long run it will not require as much water or care as St. Augustine, and you can get rid of the expensive lawn guy! Things to remember: Don't put any weed and feed down on the newly sodded sections either immediately before or after laying the sod. Don't forget to water daily until the new sections have taken hold. Especially during this, our driest time of year. If you choose to use RoundUp on the weedy areas before moving the grass squares, don't lay the grass squares directly on the area treated with RoundUp unless you put in a layer of newspaper or cardboard first. If you can get your hands on some liriope, you could make a border along the brick walk (at the top of the slope), to help hold it all together. Their roots tend to spread out rather than down, so it will keep slope erosion in better check. Lastly, don't let that man with the mower anywhere near the new section. Weed-whacker only until it's established. You probably won't need to mow this area for the next 6 weeks anyway. Maybe someone else will have a better/easier solution, but this is what I did and it works. I certainly welcome any criticism or comments on my suggestion.

One application of fungus control will not kill the fungus. You need multiple applications 2 weeks apart. Also important is what time of day you are watering. If you are only watering for 15 minutes (which is not really long enough to get water down in the soil) you should be able to water during the early morning so the grass has a chance to dry out. Does the fence shade the spot? Can you eliminate watering that area?