My experience has been that 3-2-1 overcooks also. I do 2 on rack, and start spritxing every 15 minutes after the first 30.
When I put it in foil, I only do it for about 30-45 minutes.. I depends on the meat. Then, the last hour is done back open.
The comps I have done so far in my area require that no sauce be used AT ALL. any signs of sauce on the ribs, and you are DQ'd. They say that they want to see what you can do with the meat, without actually covering up everything with sauce.
I have a nice dry rub that took about 10-12 experimental cookings to get close (and it gets tweaked each time still except at comps.)
I have seen it said here a few times, and I will reiterate it. Each piece of meat is different. You can have 2 racks of spare ribs, the same length and same weight, but they will cook different. I use a temp gauge to just gauge when i am getting close, i do not pull at a certain temp, only when they are done. You will develop the Jedi mind trick of knowing when it is done with experience.. ;)
Most of all, Just have fun and enjoy it.