I’m going to go against the grain here (I seem to do that a lot). So let the reader decide if I make sense or am just batcrap crazy
So 75 will be too warm for water. General Hydroponics even lists 75 as the cutoff point for their nutes. But in the winter, when temps are cooler (as you’re planning), you can keep the water under control. If you can utilize a cooler basement floor, preferably bare, but carpeted is ok, it will really help and is what I’m doing. During lights on, my air temps are mid 70’s -78 when my fan kicks on in the tent this bucket is in, and the temps this morning at lights on is reasonable (~70). I bought a pack of those stick-on aquarium thermometers. Not the greatest, but I’m just ballparking it when I run a DWC these days.
By definition, you can’t run a chiller in a DWC. If you do, it becomes RDWC, and then you might as well add a bucket and run a reservoir and go all the way.
Hydroguard or its Southern Ag alternative is a good suggestion, just realize it’s an inoculant, not a cure, so it’s all about prevention. If you wait until there’s a problem, then it would be hydrogen peroxide time instead.
I’ve never bought into the whole “water below the basket by X inches” concept. It makes no sense to me and have yet to see a good argument for it. Yes, I keep the water a few inches below the root crown, and never let the surface get wet once the plant is mature, but how many pebbles sit in the water is of little consequence in my book. Actually, I permanently run the bottom inch or so of my 6" baskets in the water in the RDWC in my journal. More water = more roots the way I see it. The water level in my RDWC is 5" below the top of the lid, so it could be a couple inches below a small basket, or it could be an inch or 2 above the bottom of a large basket.
Yes, DWC is one of the trickier ways to do hydroponics, but plenty of people do it, and I personally think it’s a great gateway to hydroponics, whether it ends successfully or not.
I don’t know if @ThatHydroCouple still frequents here, but he has some youtubes under that name you can check out. He has 16 I think now? DWC’s running in quite a pretty impressive setup.