1. There's no real problem with the 2550. It was just an inside between me and Malc about a previous thread on some behaviour to program this specific PIC with his PIC programmer. not much. Don't worry.

2. You can't use a PIC to PIC USB comm unless you really want to waste your time to develop a host controller... not something i would do. Hence why there's a few available on the market.

USB is not as simple as RS232 of course, it's another and really different animal.

Good luck!