Been following your axel problem and what strikes me as significant is the advice from our best-of-the-best (and your dealer!) isn't working! There's gotta be something else going on. I'm probably the least qualified person on the forum to give advice on this topic but hell, nothin' else has worked so why not! Let's try some physics. Don't know the conditions you were experiencing when the axel broke but I'll assume you were going forward at the time. Based on what you have already tried, seems like splines of the axel must have moved beyond what the socket in the tranny was supposed to stop (we'll ignore a problem with the circlip for now). Probably the only way that could happen is that either the splines or the socket are defective, that is, one or the other was not hardened to spec for some reason (my guess would be the axel)--certainly wouldn't be the first time something got beyond Polaris' QC! If that was (is) the case, seems like your options would be to either; 1) weaken the axel further by removing material (drilling?) from it, or 2) contract the axel splines by refrigeration, or 3) rotate the axel backwards so that the splines line up with the center of the grooves better.
Drilling probably wouldn't work without damaging the tranny, if you could even get a (big) drill bit in there. Releasing a refrigerant into free air seems like a very BAD idea--toxic and/or explosive! So that leaves rotating the axel in the opposite direction it was going when it broke--probably would only have to move it less than 1 or two 1000th of an inch. A couple of ways to do that come to mind. Maybe use a large u-bolt or muffler clamp and instead of pulling straight out, whack it with five pound sledge so that it rotates backwards a tad, then try a straight pull. Another possibility might be to use or make an indentation to hold a large punch at the 4 or 5 o-clock position on the axel and drive the punch forward with the afore mentioned 5 pounder. Yet another possibility is (this is what I'd try first) is use a pneumatic air hammer instead of punch/hammer in the indentation to try and get the axel to rotate/unlock.
I know I'm grasping at straws, just trying to think of other options! Good luck!