That's quite the list you've got there! Going to try and answer all of them here.
The projectile/explosion behaviour script calls:
Have you tried creating a skill with Self on the AoEConditions, and passing the character you want to hit as the source in the call? This should work in theory. If it doesn't work let me know and I'll take a look into it. As for why the ExplodeAt trick doesn't work anymore: it's using a cylinder instead of a sphere now when checking for collisions.
The source issues:
Will look into adding a source parameter to the ApplyStatus, ApplyDamage, and CharacterDie (as a nice bonus) calls. I'll also see if I can add the source, skill, and damage to the ReceivedDamage story call.
Query for status turns:
Sounds reasonable, will look into adding it.
CharacterUseSkill issue:
Unfortunately using a skill without actually casting it isn't possible, except for Projectile and Projectile Strike skill types. It's very unlikely that this will ever happen due to their complexity.
RecievedHealing event:
There's a CharacterVitalityChanged event in story.
Surface/cloud size query:
I'll look into adding a query for that one.

I hope this answers or addresses your issues and concerns smile