My mate has the same bike and hes followed me down some strong red routes and a couple blacks; his gripe is the seat post doesnt really go much lower than that without having to chop it, which means he can't upgrade to a dropper post. He's also had to replace a few parts as they've took a battering in the samll time he's had it following me down routes he probably shouldn't be doing
His knee problems have gone too but I think that was more down to riding a medium frame before. E-Bikes will help as they reduce the force on your knees whilst keeping them moving. I used to have bad knees when I overstressed them until I rode more and more and now I don't get bad knees at all even on big rides (non-ebike user).
I also have Glucosamine and Chondroitin 500mg/400mg High Strength Complex from amazon that I forget to take and only really used/remembered when I got a flare up, which relived it within a day or two
Ha. I've no idea what I've been biking on. I've just been going to random coeds and exploring. No jumps but loads of tree roots and steep climbs (thanks electric power) but it's been so fun

Where have/are you riding at the mo?