Which model Demon carb?
Are you saying to adjusted the mixture screws with the engine warm, idling in neutral @800, while watching for highest idle speed(highest vacuum), and you ended up at 7/8 of a turn?
Imo, it’s idling lower than I’d want it to.
Hot street motor, I’m usually at least 1000 in neutral.
How much rpm does it take to reach full advance?
FWIW, your readings seem okay to me.
Cranking pressure, vacuum...... right where I’d expect.
These things are always happier with as much initial timing as the fuel will tolerate.
If you can lock out the distributor, set it at 35*, and not have issues with pinging or hard starting...... just run it like that.
Though, my guess is you’ll likely need some curve in the distributor.
As a starting point I’d set it at 38* total timing, and if the initial ends up at 22-25, that’s a good place to start.
You’ll want to have full advance before whatever your normal cruise rpm is.
After setting the total timing at 38*, idling at 1000 in neutral........ engine warm, re-set the mixture screws.
I’d be pretty surprised if they ended up at only 7/8 turn.
If it still pops a little when you blip it, then it’s time to start trying bigger squirters.
If it still not satisfactory......... add 2* initial at a time.
Each time, re-set idle to 1000, then readjust mixture screws.
Whatever the initial timing is at where you feel your happy with it........ you’ll have to modify/adjust the advance in the distributor so you have the initial timing that gave you satisfactory response and idle quality, but only 35-38* total timing.
There’s nothing about that combo I see that seems like it wouldn’t work perfectly fine with 25* initial/35-38* total timing.
I know that carb worked fine on the old combo, but before I spent a bunch of time on the ign....... I’d see if I could borrow a “known good” Holley of QFT with 4 corner idle and see it it acted any better.
My experience is the Demons can be pretty finicky.