I've never built from a Maglite tube, but you need to be certain of the thread pitch. Is it an actual Maglite flashlight or one of the solvent trap sellers using Maglite sizing? Some are 20tpi and I think some are 24. Not sure if all the majors are the same, either.
Holding baffles in isn't an actual legal requirement, it's internet myth. Your end caps are silencer parts and not interchangeable. This is why you think long and hard about how you want to mount and adapt the device to your arsenal. There's a myriad of mounting options nowadays. Thread adapters
aren't silencer parts. This is why you choose the largest thread pitch, on a rear cap, and have multiple adapters. Or you can do QD mounts with a common type FH or MB.
Since it appears you've damaged your rear cap
, you should send it off to an SOT to be replaced with a modular type piece that meets your needs.
I know it's not what you wanted to hear, but I'd rather see you play by their rules than get jammed-up.