#1. im not sure about when TIE enthusiasm surpasses 5. But it isnt too long, after a few games its better to play TIE.
#2. If you play enthusiasm normal, eventually it will make its way back to 5. After a couple games, or even days, it could be back at 5, depending on what enthusiasm level you are at.
#3. Ive never gotten really high, but i have read in the forums that it has gone up to 12-14. But apparently the max enthusiasm anyone has ever played at was 12. Not 100% but its close.
Hope it helped. Im very sorry if im wrong, someone will correct me, but i am fairly new and my knowledge is a bit limited.