I'll share my RARP experience. I am a couple years younger than you, and last year I went through the same thing, with the same worries about ED and incontinence (things that aren't guaranteed to NOT happen with radiation by the way). I didn't have a single second of either.

I spent four months preparing for surgery, hammering my pelvic floor, my core and both a the same time to the point my pelvic floor therapist said she'd never felt a stronger pelvic floor on a man (you can assume how she FELT that...).

While getting into better shape, especially that pelvic floor, doesn't guarantee outcomes - it does improve them. If they can spare any of your nerves then you greatly increase your chances of ED if you prepare. As for incontinence, the pelvic floor work helps you deal with losing the one extra sphincter that men have to preserve continence and essentially just end up with what women have and they use their pelvic floor to control it.

I've never had a single accident, never a single flaccid moment when I didn't want one. I think you do yourself a disservice to not explore the best path your doctor recommends - especially at just 57. I was 54, I was told that RARP was far more recommended for men our age than radiation because we will recover faster, have better chance at fewer side effects and that radiation's side effects could rear it's ugly head in our lifetime.

That's my $0.02, happy to discuss in private messages if you wish.