A couple of things. 72 degrees overlap isn't bad, it should be showing you closer to 10-12, especially if you feed it some timing
The total timing won't change vacuum, but regardless, the Trick Flows I have used ranged from 32-35 degrees advance, yours is a bit lower compression (until the blower is connected) so I'd stop at 35-36 but bentter do check on dyno for peak power, no benefit going higher with the good chamber
Be sure your initial is right, check the balancer, set the Sniper, then see if the commanded timing reads the same as the balancer.
To adjust the timing correction once you check it, use the inductive delay section under"system parameters" "Engine parameters" and "ignition" The delay up or down will move the mark to make sure what the commanded timing matches what you read. Holley's system usually requires you to upload after every change, easy, but be sure you are doing it
Additionally, depending on your distributor, reference angle has to be right too. That's applicable for Dualsyncs and set during distributor install (but again, balancer must be checked)
After all that, the root cause I think is I'd likely be at 15 crank and something like 18-20 idle. If using the Sniper to control, the 2D table for timing is a pain at initial setup. Set it up 18/40/35 across the board using the "simple" field, and 15 for crank under "cranking parameters" then if you need to tweak areas, you can go to 2D table
