Alright, that's a bunch. Thanks for stumbling over them for me.
1: For skills in the same vein as Changelin, where what it is depends on what's equipped, there's a bit of extra structure going on in order to make sure things aren't double writing. It seems I hadn't got to that until now. You'll keep the two Changelins you have until you do the last class change, but yeah, that's definitely a bug.
2: I looked into the problem, and it seems that upon seeing that a character has a full skillset, the skill-writing script I wrote years ago just up and quits, not bothering with any skill family stuff. Actually fixing that problem is more than I can be bothered to do at the moment, so I've gone and doubled the maximum number of skills you can know at once, as inelegant the solution I ended up with is.
3: Both of those are fixed now. The suit unlocks something marginal back in Gattun now, by the way.