thats a good idea, ill see if it'll work

Maybe at settings for groups of spells (and a few important spells) to the mod config menu that way you don't need settings for every single spell individually.
Groups could be things like the following (just examples):
Normal Projeciles (cheap, weak projectiles you either can start with or are pretty common by default already)
Heavy Projectiles (stonger more expensive projectiles)
Dangerous Spells
Homing Modifiers
Add Mana (Important enough to warrent it's own group)
Explosives
Useless Spells
Divide By
Greek Letters
Digging Spells
any other group of spells you may want to make more or less common
You could then have a setting for each group to make spells in it more or less common. Outside of these groups there could be setting for adjusting if late game spells appear earlier and how much less/more common they are (or the reverse for ealy game spells appearing later).

Yes, having a setting screen where you can adjust sliders would be cool.

you're right, but in my opinion the risk of pulling in a random potion that happens to be nearby is much lower than actively using acid (an unblockable source of damage) to mine. either way, i knew from the start that my current method of hardcoding the probabilities wasnt good and im currently working on a new method that allows everyone to change them.

And acid trail is great for damaging certain enemies at any rate, combined with a mist or cloud spell it's quite safe too since those don't move unless you make them homing.

Black hole definitely can kill you, it pulls in potions and other dangerous objects. Poly in hiisi base for example is quite deadly.

yes, but black hole (which is much more common in this mod) can do the same thing, but more precise, and also doesnt kill you.

Um. Acid trail is very useful for skipping through most of the game.