Control of Campervan Heating

I have an application to manage campervan heating; based on circulating engine-cooling fluid, with the engine and auxiliary heater as heat-sources, and various heat-exchangers as heat destinations. The processor must process as follows:

a. The external power supply is a 12V DC car battery.

b. There are two analogue inputs (both are 0-12V DC outputs from analogue thermometers).

c. The processor must provide adjustable normalisation for each of the 2 analogue inputs.

d. The processor must compare the 2 normalised analogue inputs (with adjustable hysteresis); to produce a 12V DC on/off output.

e. The main processor must process multiple 12V DC on/off inputs (including the 12V DC on/off output from the above comparison of analogue-sources), if/and/or/not/then logic, and multiple 12V DC on/off outputs (for heat-sources, valves and heat-outputs).

Could you please suggest suitable Velleman components, and any other advice you feel able to offer

Sorry, this calls for a completely custom designed circuit and software.
Unfortunately, we are not into the business of providing custom solutions.