A good quality 530 O-ring chain will handle upwards of 200hp to the rear wheel.
My old '76 FHL is chain and when I restored it I went with a good quality O-ring chain.
The O-ring chain has rubber o-rings on each pin and each side. They are greased when made and have a long wear life. You only wipe them down occasionally with light oil and that's it.
I've got about 10k miles on my rebuild and I only adjusted the chain after about a 1k miles and no future adjustments have been needed.
I wouldn't swap to a chain on the M3W unless there were multiple belt failures and this were the only option. Regardless of the type of chain, they're noisy.
I still feel that getting the belt centered would be the first thing to do and forgo any sprays just to keep the belt dry and free of clingy debris.
I'd go with all of what you said. but. There is less than an 1/8" of play available for the belt to just ride on the recesses and avoid the flange. It's going to move more than that just accelerating and decelerating.
I think that the materials used in the construction of the rear sprocket is the main culprit. I was nosing around after a 40 mile test drive to see how well the WD-40 did. It held up well but I could see that it could be better. More importantly I noticed the beginnings of the sprocket slowly being eaten by the belt. It has definitely started and what that tells me is that, like the last sprocket, it is chewing at it and the debris created hastens the process. That is for the rear.
The front is a different material and shows zero wear and no displays of noise when I'm under the car and spinning things around to just see what the hell is going on. It looks beautiful and is well behaved.
Aluminum was a bad choice. H-D's use chrome plated steel. Bearings may go but I've not heard of anyone losing a sprocket!
