I had to make some fixes and it was good when peeling off, I made sure that I put on enough for that. Of course the more you put on the easier it is.

Correct, the thicker it is, the easier it is to peel. I used 1 can per wheel.

I found a place that will do it for 600.

Well less than 400 is for the paint and the gun.
It's plastidip, you have done plenty of stuff on your own, I would add this to your list.

Buy a gallon for $70ish and a wagner airless spray gun for $50ish and you're set. This stuff is not rocket science.

The 300 kit includes 3 gallons, you think 1 gallon will be enough?

2 gallons would pretty safe unless you're doing a pretty large car.

I don't think 2 gal is enough.
3 gal is pretty standard for a sub compact to sedan