a) there’s been a massive surge in black male support for Trump,
Massive? No. There's been a
small shift for Trump among non-college Black and Hispanic males, but not enough to shift the results because Biden's gains among white voters (especially women) will make up for this.
b) Republicans are beating Dems in new registrations
Two things: One, I've seen Republicans gaining among registrations, but not new registrations. So I'm not sure where you're getting this. A large portion of this is ancestral Democrats changing their registration even though they haven't voted Democrat since Bill Clinton. Two, Democrats made massive voter registration gains between 2017 and the 2020 primaries.
c) Rural Pennsylvania is under-polled
I haven't seen any evidence for this.