I think it would be a very bad day if your fin got anywhere near 'stalling angle' at high subsonic speeds
As far as I recall the reasons for sweepback are:-
More fin area for same vertical extent
Moment arm longer = more directional stability (c of p further aft as you say)
Looks cool - I mean, compare the appearance of the OLD 150 with the new 152 man!
Regarding stalling, ALL sweepbacks increase stalling angle as far as I recall. I'd have to go into the attic to dig out my text books to remember why!