Craig,
Welcome to HW.
I am not a gym/weights guy, so can't speak to exercises, but the standard suggestion is to walk a lot. I found that multiple periods of walking combined with Kegels afterwards helped me with the incontinence issues.
As to the bladder neck, you will really be looking for undetectible PSA values. As long as you have those, I would not be concerned with the positive margins, as they may or may not be significant at this time. Your surgeon is the best resource for information until the first PSA is done.