Temp problems

So I'm new to being a snake owner, and i just recently got a ball. I have central heating in my house and the temp is always set at 69 F... I have a 30x12x12 cage and a proper size UTH. The hot side substrate sits at around 90 but the cool side is usually always at 69 or 70. I got a heat lamp and that brings the cool side up to 80 but it removes humidity like crazy (ambient humidity in my room is around 60% with heat lamp 20%). So Im wondering if it would be better to get a second UTH for the cool side and regulate it to keep it at 80. Is this a good or bad idea? Also, is air temperature important or is it just belly heat im going for because the UTH doesnt really heat up the air and thats what i was going for with the heat lamp. Thanks for your help

The hot side should be 90 at the surface of the terrarium not on top of the substrate IMO. If you need the heat lamp you can get a small shoe box and fill it up with water and put it under the heat lamp. And use cypress mulch or something to keep the humidity high. What kind of cage is it? It it's a glass tank with a screen top put damp towels on top (avoid the heat lamp)! That saved the humidity in my tank! I also would move the water bowl under the lamp

Any heat source that heat the air for ambient temps also will alter the humidity. A second UTH will not heat the air and this will leave you with a different issue of too low ambient temps. The solution is humidity management the idea of a water bowl under the lamp is a fine one this will also act as a thermal mass and help to hold temps and stabilize them.