My trick: if it gets too hard, let it sit, and get back to it. My balance is also different than your balance.
Balance is very very hard
I've been focusing a lot on balancing this game and man is it getting frustrating.
I just spent three hours trying to make the splash damage system more fair. It's still probably going to receive some revisions at the moment enemies get pushed too much from explosions and this can be abused on early levels. Later on as there are more enemies this becomes less viable. I'm having a lot of trouble balancing this mess as I have from the beginning. Hopefully I will eventually be able to reign in this game.