Did you try to put a jumper on the circuit breaker? Turn the power off before doing that.
Have you checked for 240VAC across the bake element contacts with oven set to BAKE?
Take off one wire from the element, check which side doesn't have voltage (120VAC) and trace it up.
You already replaced the relay board, the temp. control. Check the selector switch Part number: AP3912099
There is a possibility that the parts you replaced are bad.