I would recommend that you speak with a local ffl/sot concerning the specifics about local law or any other questions that you may have.
I'd recommend using a gun trust because you don't have to submit fingerprint cards, you dont need a CLEO signature, and you can add people to your trust so your friends can hold or shoot it without it beeing an illegal transfer by the ATF's definition. To set up a gun trust make sure you use a competent attorney and not a program like will maker, because if it's not set up right you can get into some trouble.
To register the nfa item to yourself you will have to submit fingerprint cards, get a CLEO signature, and of course pay the $200 tax stamp. Doing so in this method means that your friends, wife, or anyone else won't be able to (technically) legally shoot, pick up, or touch it technically. Also, if say you are at public and your wife's home,you have to lock up the gun and keep it out of her possession. With the trust, you can add her to it and she can take possession of it without being an illegal transfer.
Any competent gunsmith can chop and crown a barrel, you don't need a sot to do it because the lower is the sbr. Just make sure you have registered the lower as a sbr before you have a short barreled upper in your possession ( it can look like intent to make an illegal sbr).
I'm not going to give legal advice on what forms to file or how to file them, that's something for a local ffl/sot or a Lawyer.
Good luck on your sbr.