For me, everything goes off the rails character-wise at the party. The first time I actually managed to trigger his romance, I was really enjoying it until this one-two-three punch:

1) After some minor flirtation and stalling the PC romantically for days, on the night of the party Gale decides to go from 0-60mph in terms of physical intimacy, even if the PC has explicitly indicated that they want to take things slower. It's either sex or the end of the romance.

2) The next morning he reveals that he's still-maybe-probably in love with someone else. A goddess, no less. AND he hid this from the PC because he knew it might be a problem and he wanted that sweet booty.

3) Immediately afterwards, he reveals that he's a walking high-yield explosive and a serious danger to everyone around him, especially if those people are ignorant of his explosiveness. Which everyone basically has been until that moment.

One of these things? Not so bad, I can work with it. Two of them? Eh... sketchy, but I can make allowances. All three? Gale has crossed a line in the sand for me. YMMV, of course.