The difference between a neutral and a good character is in their motivation. Neutral character cares more about themselves while good characters care about the others. Gale puts the safety of others above his personal desires, as he states he'd better blow up in solitude rather than threaten the lives of others.
-snip-
[list of "Good vs Bad Things"]
I wouldn't call this putting the safety of others above his personal desires. It's more: "if I'm almost certainly going to die, I don't want to kill a bunch of people along with me." Which is nice, sure, but not Good. At this point, when he knows he's going to explode in the next few hours and almost certainly can't be saved, there's no real cost to secluding himself.
Similarly, most of the positive things in your list don't come at any significant cost to Gale, so they're more him being nice than Good. He's certainly closer to Good than to Evil, but I'd still peg him as overall Neutral, as not much indicates he'd sacrifice things important to him in order to help others.
If anything, I'd say the single Bad Thing on his list (making a deal with devil to preserve his own life) shows more of his Alignment than practically any of the Good Things.
