to much humidity in a tub?

That's not bad, though it is still slightly on the high side. If you can try to get it down even further, like maybe 60% for ambient, it would be better. You'll also have less bacteria build up. The higher humidity with the required BP temps just create a breeding ground for it. :(

Are you using a rack? If so, it looks like you are measuring the humidity on the cold side of the tub... condensation will build up there because that is where the cooler temps from the house meet the tub. The average humidity in the rest of the tub won't be that high.

IMHO, for ball pythons you don't need to worry about humidity in a rack. Keep it clean daily, use a properly sized water bowl, keep the water bowl fresh, and allow some ventilation and your humidity will be fine. If it gets too humid and you see condensation on the walls, clean it! this normally only will happen if water is spilled, the snake pees, or you don't have any ventilation holes.

In a rack, nothing is easier then plain old newspaper for the substrate. It does not increase the humidity. And, unless you dump out your aspen daily, newspaper IMHO is the healthiest, cleanest option for your ball pythons.

I didn't want to start a new thread because I'm having almost the same problem and my tub set-up looks exactly like what the OP has.

The humidity in my room is ~35% and when I put the lid on the tub it seems to go right up to ~80%. I'm using a layer of newspaper with some aspen as my substrate and it's dry. FWIW, I've had my snake for less than 48 hours. And it seems like I've read somewhere that humidity can spike early on and can settle down later. Don't know if that's true or not.

The first thing to try would be a smaller bowl and more holes in the lid?

Had the same problem, make a crap load of holes. You wont loose your temps, and if you start having problems, or need more humidity. Just cover a a few holes with duct tape. whala

I just got home with a smaller bowl and put some more holes in the lid, so we'll see how that goes.