Hi!
The plumbing looks good...but I prefere a third line going parallel to the fule intake line in the tank (Called Uni flow set up).

It sounds as if you run ithe engine too lean! Open up the highspeed needle somewhat and try again. The engine should never rew max when you hold it straight up!

You say you can't prime the engine without blowing in the pressure line (pressurizing the tank)This sounds like you have set the low speed needle/idle needle too lean ...screw it out just a quarter of a turn and see what happens.

Regards!
Jan K
Sweden