Yes, stress and anxiety can cause itching

No way should you be doing the bridge exercise!!!
There are lots of gentle exercises you can do to strengthen your core muscles to start out with. A PT would be more educated than I am on that tho, so I won’t make any suggestions.

The recumbent bike should not hurt your back, but I would cut down on the time you are on it to maybe 5 minutes or less for now if you are having trouble walking

I’m so sorry you are having such a hard time right now, Bobby (((HUGS)))