Sounds like you have bearings problems that need need grease. Normally the drum rests on two separate bearings up front and one located at the drum center at the rear. Since you know how to take it apart you should be able to locate the bearings. A mall amount of general purpose grease will do the trick. The scatching noise may come from loose object floating around, may be a shirt button ? investigate.
Good luck and good repairs. A dryer repair is not too difficult since you have already checked to condition of the belt...Here an extra tip for the performance of your dryer, always clean the screen air filter with soap an water to remove the invisible screen deposit by the Fabric Freshner Sheet also called Fleecy. This will allow air flow to exhaus the dryer more freely.
you'll have to call in a tech to check it out or replace the dryer,nobody can answer that question without being there and checking the dryer with a meter,if the wires from the timer touched metal and i can't see how that happened unless someone worked on it without unplugging it you could have cooked just about any wire or part that those wires go to but then again you could change the timer and it could work but you have to check it with a meter first,that timer cost around 140 dollars,to much money to just guess at.