The situation you're describing is impossible. The carb bowl is vented to the atmosphere, so no pressure at all is able to get past the needle valve, and back into the fuel line. Blowby doesn't get into fuel lines- - - -period! The crankcase is also vented- - - -either to the atmosphere directly, or at least to the "clean" side of the air filter. Have you made any measurements of battery voltage and/or current draw while the engine is refusing to crank, or are you just guessing at what's happening and throwing random parts at the problem?
Jerry
