Have you read through my how-to on this form? It’s in the Work In Progress sticky and answers several of those. ETA: link

1. Use current address. Even smoother if that happens to be the address of record (from the Form 1)
2. Give yourself plenty of time. They’ll take dates up to a year. So if you have a decent idea of when, request a month (or two) before and after then.
3. They’ll actually take either. I usually use the info from the F1, so the mfr on the lower
4. It is a working firearm...so Yes
5. Keep it simply “permanent change of address” (which is actually the example used on the form itself)...they don’t need to know why you’re moving
6. Just put “personal vehicle” as long as you’re not paying somebody to transport it.

You can definitely go to a non-SBR config and move.

I’ve seen people make the argument that you can do what you said about reconfiguring in the new state. My question would be where’s the paper trail to prove you were allowed to have the NFA item in the new state?  Odds are it would never be questioned, but do you want to be the one that tests it?

Could you put the short upper on a pistol configured lower? Or leave it with somebody else to send it to you when Form is ever approved?