I have a desk with a section for a PC. The problem is my case is pretty tall. I'd have maybe an inch and a half of clearance above it. The case has 2 fans in front, 1 in the back, and 2 on top. I'd put it on the floor if It wasn't carpeted. Thank you!
You're fine. The fan in the back is the only one getting air out of the case, so having 2 fans with "not great" airflow is not really gonna make a difference. An inch of clearance is generally the minimum, think of how your power supply can get air from the bottom when it's only raised an inch from the floor.
Depends how hard you plan to make it work, and if you intend to overclock it.
I recommend just building it then seeing how hot it actually gets. Realistically you'll probably just find the fans all turn faster (making more noise) and that you should clean the dust out a bit more often