It's ok. Try to not stress it too much. I know what it is like to be completely dependant and attached to your phone so I know the situation sucks.
The trooper typing comes back becasue of a service book that is sent by T-mobile. You may try going in to delete the service book for trooper typing first, and then uninstall the program after doing that. I have actually not looked into do this yet, but that should work.
What problem are you having with the 4.5? Why are you going to go back to the 4.2? I have the 4.5 and it does work quite a bit better. I would encourage you to try it out for a while unless you absolutely cant handle it. What exactly do you need/want out of your phone at this point?
You can PIN me, and ask me any questions you have.
..the final frontier...