It's really difficult to diagnose problems like this over the internet. Your best bet would be to take it to your local hobby shop or get an experienced friend to help you out.

With that said, if your slide is rotating, it sounds like your idle stop screw has backed out. There is a grove that the idle stop screw rides on and if it backs out too far, the slide will be able to spin around. You need to tighten the idle stop screw until you get the idle set correctly and then get the tune right and it shouldn't overheat any more.