When I see black in a carb, I immediately think backfiring... more typically that's an issue with timing/distributor adjustment or wear/timing chain wear.
Crankcase vapors should be drawn downwards into the manifold rather than going the opposite direction.
If the PCV valve or its hose or the nipple into the base of the carb were completely obstructed, the crankcase vapors could blow back through the crankcase inlet oil bath air cleaner, then into the main air cleaner and into the carb. There would be a pretty obvious oily staining around the crankcase inlet air filter hose at the main air cleaner nipple if that were the case. If the crankcase inlet air cleaner hose is dry and non-oily inside, the vapors aren't following that path.
I'm not familiar with that carb, so I don't know the choke adjustment specific to it, but if it's actually a manual choke, the actuating linkage/cable should probably get you from completely closed to completely open as you draw on it; on any normal carb the choke plate should be wide open during normal warmed up operation. You'd close it for starting, then draw it out slightly during warmup.
BTW, in your original post the underscoring and photobucket link for your last picture had gotten tangled up, so I fixed it for you.