Code P0442, CAN Bus Off and large EVAP leak?

Also the number on reason evap problem is a loose or bad gas cap check it to see if it leaks look at the rubber seal if its crack missing dried out leaky or if the cap doesn't tighten properly replace it. Check all evap tanks and hoses at the gas tank and engine compartment for loose leaking cracks or disconnected listen for a hissing sound especially down by the fuel tank check all hoses there. Check all evap devices plugs wires connectors pressure control valve
You said you changed the purge valve that might have solved the problem already after going over the rest of the checks. I'd erase the codes and drive it and see if any codes come back, they might not.