There aren't any seals in the throttle shaft. The only way you'd get liquid fuel out of there is if the float level is too high and/or the floatis compromised, and its either overflowing into the venturi, or dripping out of it onto the throttle plate, then coming out around the shaft.
I'd go back and check that float level really closely and be sure that the float isn't coming up so high that its hitting the top cover and keeping it from closing off the needle valve completely.
Also check the needle valve: Is it the Viton tip needle (looks like a rubber tip) or metal? I find that the Viton tips sometimes if the kit is a bit older tend to get stiff. I also find that if you sort of "pre-seat" the needle into the seat with a light pressure before installing it, that helps it to seal a little better.
Is the float brass or phenolic plastic? If its brass and has a very tiny leak, it could also be losing its ability to float. Give it a shake next to your ear and see if you hear fuel in it. Same goes for the plastic ones although they can be harder to spot, because they act like a sponge and soak up gas reducing their ability to float. You have to weigh them to determine if they are soaked with gas.....or just toss them and replace if you suspect a problem.
There isn't any reason that at 2 PSI if everything is functioning properly the needle should be unseated.
"Free advice is worth what you pay for it."™