I picked up one of those filler funnels and noticed the same issue as you, the juice doesn't go anywhere, it just sits in the funnel. I now just use the slap yo mama tank tool, works much better and has other uses (inserting carto into tank to save o-rings)
As far as your tank issue, it doesn't sound like a tank issue at all. It sounds like a carto problem or a juice problem. The tank is just a reservoir of juice, feeding of juice is the job of the carto. If your tank isn't feeding your carto, your juice could be too thick for the size of holes. A slot might work better for you than a hole. Smoktech's pre-punched cartos have holes that are a bit too small for some people. If you get a cheap carto punch, the kind that's just a ring with the thumb screw, you can widen the stock holes. Or just buy new cartos and punch them yourself.
Either way, you need to be looking at the carto and the juice. 50/50 isn't too crazy thick or anything, I know I've used thicker juices than that with tanks, so the problem is most likely with the carto. Again, could just be that the holes are too small, could be a dud carto that for one reason or another refuses to soak up juice from the tank.
I've had some cartos, brand new, that stay flooded 100% of the time when in a tank. The second you put them in there, they just continually bubble and flood the heck out of the carto. I've had others that did just as you describe, they would refuse to soak up any juice from the tank unless I went to great lengths to help it along (many many many very strong dry pulls). Smoktech cartos seem to be lacking in consistency compared to other cartos out there.
Sorry for being long-winded, but in short, throw a new carto in there, or widen/add holes to the carto. Like I said before the carto is the only piece of the tank actually "doing" anything, so the tank isn't at fault for things like bad performance or feeding issues, the carto is. Play around with different holes/slots of different sizes if you still have feeding issues with a new carto.
Hope this helps!