Are you sure the pieces are
Are you sure the pieces are all compatible with each other? If yes, you can; if no, you can’t expect to get a sound result.
If they are all compatible then you can fire them as they are, no breaking up or not.
Any additional glass has to be compatible with the other pieces.
The firing schedule does not need adjustment. Normal schedules are designed to keep the pot whole. Ceramics have different characteristics than glass when being heated.
If you can find compatible clear glass, you should add quite a bit of it. I find that at least 50% clear gives good results. (Unless you want an opaque result)