You will definitely need a way to reduce the current of your J1772 device.
Some 14-50 outlet at campground or public place are not properly maintain and trip the breaker at 32A.
About 12V power, do you have an idea of the power of the inboard DC-DC?
Your project seem awesome and I have to say that you are brave to do this considering of the low reliability of those ''old'' Lion electric bus.
Do you have a thread/blog to see the advancement?