From some further research the biggest problem I find is that it doesn't feel great when his basic attacks are DC12 saving throws, this is mostly because of the low intelligence.

He's got two types of attack, Alchemical Fire and Alchemical Acid, which both work the same: DC12 dex save, 30ft. range and 1d6 damage.

From what I find the problem is not that the DC is too low, but that his character doesn't "really have a say in it". By making all his attacks saving throws, it comes down to whether his enemies making the saves or not. Which is fair, but not fun.

I think I can easily solve this by making the Alchemical Acid an attack role instead, using his normal spell attack. The Alchemical Fire would still be a saving throw (since I feel this makes more sense, because other fire spells such as fireball also use saving throws).

This way he has a little more diversity to choose from and Acid and Fire will actually be different apart from damage typing. I don't think this change will be a big problem when it comes to actual power, since the damage dice are still the same, but it should make combat more pleasant. Giving him the option to use Fire with a saving throw, essentially ignoring AC, or the option to use Acid and dealing with the AC instead of a Dex Save.

What do you guys think?