I did not screw my mobo back in case my TSOP write points were not being detected.

Now I want to put it back together, but I came across a problem due to my level of excitement.

Any tips to remove a stuck screw in the case?

You mean you stripped the head of the screw? And now it wont come out?
I would (CAREFULLY) drill straight through the head and make a new hole through the screw, then you can pull the head off.