Ok, the attempt at de-soldering that bent stub was somewhat successful...however, instead of just the stub coming off...the other end of the fitting came loose, too. just no way to heat only one joint on a tee, without heating them all, I guess. So I took the whole thing off. there appeared to be just enough of a stub left sticking out of the next tee over to the left, so I cleaned up the pipe ends as best I could, and tried to replace with a sharkbite tee. It seemed to hold...so I assembled the pex to threaded connectors with the check valve, and worked it into place. I thought maybe I wouldn't need an elbow, but these big fittings do take up alot of linear real-esate. by the time they're all linked, the corner to bend was too sharp. no problem...I picked up a 90, just in case.
outside, I had to drill a new hole to mount the drop-ear...that was a pain. But once I got it all put together, the only leak was in the threaded fittings with the check valve. (very slight "weep"). no problem to give them another half a turn, as the push-connector side can still spin free...and I can reach everything now. and even if I couldn't, it'll all pop out of there very easily.
the reason the original vertical section of pipe had a split:
well, the check valve that was in place in there, burried and inaccessible, hasn't worked since I've owned the trailer. As a temporary measure, I bought a replacement, and instead of installing it where its supposed to go, I just threaded it onto the drop-ear elbow at the inlet. that worked...but the flaw is that it holds water in that riser, and that water won't drain, until the check valve is removed. I did this as part of my winterizing routine for the last couple of seasons, but this past fall, I got sidetracked, and we had a very early cold-spell. mid-winter temps before thanksgiving. so...live and learn.