feel free to check my code 
I have used some of yours for the sensors.
I have also used an algorithm for the temp sensor which could be useful for you.
I plan to rely on the ECU data mostly yes. I will expand the compatibility to standalone ECUs for race cars as soon as I get my hands on the protocols.
Also, I might switch to a bigger LCD, with T6963 controllers, which has some interesting hardware drawing functions as well.