carbed out

^^ x 2, Well at 15* you might be close.
But here's the thing.On the Holley. With the throttle blades closed, ALL of them, there is no way the engine should idle. I wonder if the secondaries are stuck/adjusted partially open, or if the choke cam is engaged. To have the curb idle screw all the way backed out, AND the mixture screws unresponsive,AND the idle still at 500, says the engine is getting air and fuel from somewhere else. And in just the right amounts.While set up as it is now, temporarily throw a rag over the secondary side to block it off. The engine should stall, proving the secondaries are feeding.That's not good.
With your manifold vacuum, I'm pretty sure the secondaries can be FULLY closed, but not sticking, so make it so. Then, make sure the choke cam is parked. Make sure the Transfer port is synced.Reset the mixture screws. And try again.
A leaking PV will usually flood the engine to a stall.

Average of 155 psi is a very good sign, as is the 3.55 chunk.So; you have adequate cylinder pressure, and a good gear. After we get this beast running, we'll do a stall test to ballpark that. And then it's tuning time.