Hi Pom,

good to see that you´re making progress!

First of all I would like to know which printer board you´re currently using. I wouldn´t recommend a heat bed control seperated from the printer electronics since I don´t know any software supporting such a feature. Usually the temperature of the hotend AND the heatbet are set automatically at the beginning at any print job and afterwards both will be swichted. I wouldn´t want to loose that funktionality.

I think many of us using the Aduino Mega (or a clone of it) together with RAMPS board. There is a good documentation available for this combination. Firmware could be Marlin which is good described as well.