Thermostat upgrade help

My concerns about the Dometic single zone digital tstat and control system continue to grow. I'd never switch to this from something else. We had the complete control replaced just short of 3 weeks ago. Today I've seen as much as 8 degrees difference on the tstat before the AC kicked on when running in auto. Then it would kick off with still 3 degrees of difference. It will not run on low fan--as soon as the compressor cycles off, then the fan shuts off also. The ONLY way this thing works right is in high fan mode where the fan roars at full speed and the compressor cycles on and off. The temperature control doing it that way is actually close. In addition, Dometic RV products must have the rudest customer service people on earth. I got transferred to the wrong number numerous time, and just plain disconnected once. Rather than spend the $$ on another set of electronics, it's time to mod it like a home system.