While I'm sure there are those here more knowledgable than me on this subject, I'll weigh in.
I would have no problem using a barrel band swivel assuming I removed the sling when I got to the blind. I can't help but think that you would effect the harmonics of the barrel depending on how much stress you were putting on the sling while shooting. That being said, would it effect your point of impact at ranges less than 100 yards? Doubtfull, but only range testing will tell for sure.
As for the bolts coming loose, I'd check to see if they are bottoming out on the barrel. If so, remove a couple threads with sandpaper or file, then try them again. You can tell by shining a flashlight in the threaded impressions and see if there are little silver circles scraped on the barrel. If they're not bottoming out, then I don't think Loc-tite is a bad idea at all. Personally, I torque mine to 18 inch pounds and have not had a problem with them coming loose.
Good luck!