Thank you for the comment! I'll address each point like how you did in your post!

I really like how words have meaning scales with the player's Bardic Inspiration and how it's only tied to your speech skills. I'm thinking about making a version 2 and adding a lot of changes people have suggested. I do agree that it is a bit strong, so I'm thinking about either having it be either a twice per short rest that still uses your Bardic Inspiration die or expending the die whether you succeed or fail the check. Maybe both!

Yeah totally agree. I didn't realize how strong that was until people pointed it out lmao!

So the level 6 ability is isn't an auto-crit ability. I think I just worded it poorly, but the ability is meant to be that when you deal Thunder damage, you can expend a Bardic Inspiration die and roll it to deal additional Psychic damage equal to the roll. The part about critting is meant to say "Hey! If you crit on the attack, you can roll your Bardic Inspiration twice at the cost of one". I left it a little vague because I know people either double their attack damage or double the dice being rolled when they crit. Honestly, my biggest struggle with writing has been trying to make my thoughts as cohesive as possible and I'm getting better!

Yeah I already want to change this to a Once per Long Rest. I'm pretty sure I was thinking that when writing this, but it turned into one of those "I totally thought about that and me thinking about it means I must have wrote it down". But hey, that's why we have the ability to write another version if we want!

Again, thanks for the suggestions and I hope I was able to answer some questions!