The hot side not "feeling very hot" doesn't mean it's not hot enough to burn your snake. I'd run out to get a lamp dimmer NOW ($9 at Home Depot) and put your UTH on that until you save up to get a good thermostat.
You could black out 3 sides of your tank with black construction paper to make him feel more secure too: or I just put a towel over my corn's cage when he's in shed to give him some privacy (he's my only snake in a tank, everyone else are in tubs).