1. I live in Texas, so my concern was air-conditioning

If you're curious, I bought 2 24Kbtu window units with 15K heaters built in to the AC units for the one or 2 days a year I need em for out in the shop. (Have an insulated 30X40 steel building in the backyard) You can't beat window units for the price and convenience (install em yourself) but if you're out there a lot, they are not the most efficient. Though I do run one unit if it's not too hot, then turn on the other if needed., which is nice. In my garage in my house, I have a mini-split with a heat pump I picked up off Amazon. (Can't have a window unit sticking out of my house in my neighborhood) Installed it myself... It's pretty efficient, costs more than the window units, but did not cost as much as a full blown, installed system.
2. Have a bunch of T8s... Installed them on different switches, so I don't need to light up areas I'm not using. Think I did 5000K color as well
3. Have had a lot of luck with
http://www.adpolymers.com/ for floors... Done several garages as well as my workshop. I did a low build floor with 2 coats of aliphatic epoxy base and 2 coats of urethane top coat for my shop in light gray... Really brightens the workspace, easy to clean, good with chemical spills... Even stands up to MEK, at least if you clean up quickly.... MEK eats most floors other floors I've used almost on contact. I did no chips in the workshop, but have used them in my garage. Both have been in place 8 or so years, and still look great. If I had the $$, their high build systems look great... (Basically the same as the low build system but with a high build intermediate coat you float out over the floor) But I can't justify the cost for something I'm going to drive on, drop tools on, etc.
Also, seems to do ok with light weld spatter.... Though I do use a weld blanket if I think what I'm welding's going to throw a lot of slag...
Remember, paint quality is all in the prep...
4. I agree, DIY benches
5. I have a Gemini 2 post lift... Not high zoot like a bend-pak etc, but they are local to me (Fort Worth) and in 8 years, not a single problem. Lifts my Excursion, like it's nothing, too. HIGHLY recommend getting an asymetric lift if you go 2 post. Much nicer not banging doors on the lift columns...
6. I plumbed my shop with 3/4 PEX and sharkbite fittings... FWIW, these are not rated for air, but I read somewhere that sharkbite (or one of the fittings suppliers) uses this same sort of setup to feed air in their manufacturing center... Just run it out of direct sunlight as I think PEX is not UV stable over time. Easy to add on to, as well. I've seen burst tests with PEX... the the pipe just splits.. No fracturing/shrapnel like PVC... Also, did not see you mention 220volt outlet for a compressor.... Lifts are usually hard wired, and if you try to share the welder receptacle, you wont be able to run a plasma cutter (needs compressed air and 220 volt) Would also run 220s for AC, but you probably don't need it in IA.
7. +1 on the fridge... I have a sink with one of those on-demand-hot water heaters... Use it more than you think. I run the hot water through my powerwasher... Sort of a poor man's steam cleaner. FWIW, I ran an air line from the shop back to my house... That way I can use shop air in my garage...
If I had to do it again, I would love in floor lighting under the lift... Built right into the slab. Haven't done much research into it as that ship has sailed... Been looking at doing some sort of floods mounted to the floor near the lift columns...