NO don't block your crank case breather whatever you do. The only thing you need to block iirc is the nipple on the underside of the inlet mani.
That L shaped piece is very common to split so get yourself a new one plus new O ring. Rip out everything you see in that pic and run a 19mm hose from your crank case breather L pipe to your catch can along with the upper breather from rocker cover. Use a piece of hose to replace the one from inlet to brake booster.
I know you've got your own crazy setup on your car but everything you need to know is explained in that link I posted
Steve