1. trans cooler should be good, i haven't heard of anyone having over heat issue with the trans.
good to have it.
2. competition rad is nice to have, but not a must, it is quite expensive, so it's your call
3. yea 7at should not be hammered at 5th 6th or 7th if you don't have a built trans, people have had issues with this. You can simply adjust your driving style to accommodate this issue, just down shift
uhm hard to say. Mostly use gears 1-4, gears 5-7 use freeway mostly.
4. depends on what oct tune, with 93, you should be looking at the range between 390-430whp for stage 1, 480-510 for stage 2. however if you want to go on 91 oct, that number will go down by a bit, check the press release by GTM for examples. Fuel mileage is not good, i'm having a hard time to get over 230 miles per tank with DD driving altho most get over 250 but hardly over 300. on the highway it can get a bit higher.
I get over 300 a tank. Before I use to get 350-370.
5. only advise i can give is to make sure that you know what you are getting into, it's not always smooth sailing, with these kind of extreme mods, problem will arise, prepare for them. also make sure there is a shop near you that you can trust for install and support when stuff needs to be replaced.
Please get a custom tune. It will help the car alot.