Interesting concept, but I don't think it's quite the right flavor for source. The skills actually do a pretty good job of making you understand why it's such dangerous magic.
Its about readability of skills. Game mechanics. Not about sourcery lore. A system of skills which contains a lot of spells you use once or even non is not readable. A player will always has a feeling that there is something wierd or bugged or not balanced.
My proposed solution is aimed at lowering number of skill. Generally, less steep learning curve for player.
Look at darkest dungeon. 7 skills per class. 4 skills in a battle. Every skill has 5 levels of power.
Clear readable system. Try to describe DOS2 skill system in a 3 sentences.

That is the core design thing which should be fixed. Hopefully it is not too late.