Of course you have to drive it to get it dialed it! It sounds like you need a different spring rate than what you currently are running. Stiffer sounds like the way to go since you stiffened things and they improved. Just keep it balanced. As I said, balance is key but there is no one frequency that will work. I am telling you an order to do things in and what to look for but I am not telling you the actual setup. It's up to you to determine that. Get some stiffer spring rates and try it again. You'll get there but now you are learning some things to look for.

You've found out that it drives well but bumps are a problem. You are narrowing problems down. That's what you do with tuning. The problem with the approach that many have to tuning is that they will fix a problem in one area but at the expense of something else, even if that isn't apparent right away. I don't see failure here. I see a lesson. You've learned that you need stiffer springs.

Don't give up yet. A good tune is slow and methodical. Stick to the method and address the issues as you see them. You've found one!