As for the shed, it is OK to have some left on the head, but there is a sticky at the top of the forum that will answer how to remove stuck sheds.

As for the feeding question, if you are feeding two mice at a feeding, it may be time to step up to rats. It should heal on its own if there is no cut, but if there is a cut on the snake, it could require further care.

You probably worrying too much, but we all did with our first!