28* initial timing for a 318? How can that be?

I am new to tuning my 340( ld340 intake, headers), unsure of what cam is in motor (more lope than stocker), unsure of actual comp ratio but its a 69 340 with 894 heads, electronic dist, vac advance not connected. Bought it like this. Doesnt hestitate but seems sluggish till about 3k, heard it ping on 93 octane uphill under full throttle at top of 2nd gear on hot summer day, retarded 2 degrees(32 ALL IN) doesnt do that anymore. Edelbrock 600cfm, idles @ 650-700 in d and 750-800 in P or N.
from what i gather i need to remove carb and ensure t slots are correct gap(35-45 thou) with idle speed screw, reinstal, turn dist advancing until i reach the point where idle stops increasing? so what happens if its too fast OF IDLE THEN? if i cannot reduce idle with idle screw as that will change t slot gap? or do i just adjust dist until i have 800 rpm or so and thats my initial? I finally found a shop in my area that has a dist machine, i want to recurve based on MP performance curve, i want to regain vacuum advance for efficiency. i think the edelbrock carb is perculating fuel as it has a very thin gasket and gets very hot to the touch, uncoated headers dont help underhood temps. so many variables but i have always been inclined to adjust timing first, then carb when tuning. plugs look ok, a little rich if anything but they were accell 494 plugs and i changed them out to NGK BKR6E. Vacuum at idle is 13-14", max vacuum is 19-20" driving.
Read this entire thread, more confused as ever as i dont know cam/build etc.
Just gonna follow these links i found in other threads and learn this motor is my guess. There is no right answer, just looking for correct sequence to find best tune without getting pulled over during repeat testing while not paying gobs of $ at a far away dyno.
https://www.forabodiesonly.com/mopar/ams/distributor-starting-point-for-a-curve.182/https://www.forabodiesonly.com/mopar/threads/holley-idle-mixture-screws.461728/#post-1972952509https://www.forabodiesonly.com/mopar/threads/performance-timing.451809/page-2#post-1972783761