In the spirit of posting every two months ...
The back is "pretty good". The neck is fine. Sometimes, lots of active recovery methods are needed. Sometimes you just need to rest. For weeks. But, keep building the desire to "get back to it".
I've been doing substantial mountain biking (on a new 29er). I'm -- just this week -- starting back into some calisthenics and using a lighter kettlebell. I think ETK ROP (ha! look 'em up) will be my ticket to build back up to some strength work.
I can't imagine *starting on* heavy for at least another two months (beginning of October). That would work well as mtn. biking season would be starting to wind down.