It's kak - toss it. Do as you thought and run a tube from the port to the chain.
A check valve is a worthwhile addition. The duckbill rubber is the same Indian pre-rotted kak as the intake manifold rubber, good for maybe 3 months out of the box. Walmart has a $8 check valve that works just fine. Probably a PCV valve from the auto supply would be better and more accessible to you.
I think that white foam is more from H2O in the combustion gasses leaking past the rings. Re-ringing with cast iron would give you an excuse to visit the head gasket leak. Order two sets in case you break a ring on installation. Use lots of rags to block debris from finding it's way into the crankcase.
If you aren't tight on funds I'd recommend H's alloy barrel & fitted piston, 500 or 535 with the 8.5/1 forged slug. Bullet Whisper says the stock bottom ends seem to hold up fine if you aren't abusive. The forged pistons use steel rings, so outlast the cast versions by considerable margin. My engine now makes hardly any white foam with the new forge slug I installed, and the metallurgy is way better. No more concern about the skirt popping off and dropping into the crankcase.