Recommendations:
Once thing at a time, at 3 weeks you have a lot of healing to do yet. Slowly but surely become as active as you were prior to the RP. Do your kegels, lots of kegels LOL. Try to get your quality of life back as best as you can.

PSA has a 3 day half life I believe, don't expect too much on that first blood test, what's important is that it's going in the right direction. If it's undetectable or not depends on how high the PSA was when you had the surgery.

"..the tumor was contained within the prostate and both lymph nodes and seminal vesicles are free of cancer.."
All excellent news, take the win here.

Unfortunately the invasions aren't good news, but, they don't have to be bad news either, all depends. If the Pca cells found in the margins and Perineural tissue are all there was, the surgeon may have gotten it. If it got past that point you may need some follow up. Monitoring the PSA will give you the indicators that you need.

Didn't the doc(s) have this report when you had your cath removed? What did they have to say about it?

I realize what you're dealing with, been exactly there. My best medicine at this point was work on my recovery from the surgery and enjoy myself getting back to normal activities as best as I can.