Personally I'd leave it be. 3 years and the snake is healthy the temps are fine. If the temps were not fine the snake would be sick dead or dying.

There is no right way to set up an enclosure just ways that work and ones that don't. No enclosure is the same nor house is the same. I am a control freak personally it colours my responses for that I am sorry. I don't like my enclosures varing unless I choose to do that myself. Yours does but unless there is something wrong with your snake there is nothing wrong with your methods.

try the coco husk it may help the humidity or a humidifier near the enclosure. With the time you have had the snake if it is healthy feeding and growing normally your temps are fine. The easiest humidity solution would be a humid hide the snake will use it when it needs to.