First thing I would do is take apart and re-assemble the carb with a piece of fuel tubing over the needle valve where it meets the barrel.
I have an even older TT GP 40. Yep, fuel and oil (mostly just oil) will spray out of the front bushing. Always has and always will. It can be a little messy but part of the reason it comes out is for lubricating the front bushing.
Opening or closing the air-bleed hole will only affect idle. The hole gets closed off by the throttle barrel at about 1/4 throttle.
If you decide to open the needle jet hole a little be very careful. It won't take much to muck it all up.
As others have said, sealing all possible airleaks around the carb and needle valve is the first step to success.
During re-assembly are you sure the cylinder sleeve was put in it's correct orientation? Just a thought.

Good Luck