Nature-based works for healing magic, though healing spells could really just be however you learn it.

Unless you're actually making something for the setting, you should not assume it works how you assume it does unless directly stated. Star magic is... not healing. There are many religions with varying numbers of deities(Tanya is a devout paladin of the Church of Reon, which has one chief deity and a secondary one).

While not stated, dwarves are most likely ancestor worshippers or something like that.

However... your backstory for one thing is honestly very questionable at best.