Hi,
Your probably not going to like it.
80f is fine for a cool end but is in no way acceptable as the only heat level they have.
They need a warm end of around 92f. Otherwise you are going to have serious problems as they might not be able to digest their food properly which will lead to regurges as the rat rots inside them faster than they can digest it.
So I would say try the dimmer if your house temps are relatively stable - but if they fluctuate a lot then dimmers will very quickly drive you nuts.
I only feed small rats to even my adults on a 7 day cycle.
How are you quarantining the new snakes from your existing ones - because it looks to me as if you have forgotten that step in your plan and I'm not really a fan of that.
dr del