I have a standard 454 chevy with a demon 850cfm single with vac secondaries. Timing is at about 34.

Originally I just threw the carb on it and ran it. It would choke itself out as soon as the secondaries opened up. Turned out it had 67's in the front, 75's in the rear.

I bumped it up to 80 front / 81 rear to see if it would fix the issue, which it did, but now its running super fat.... tons of exhaust soot all over the transom. I havent even bothered pulling a plug to read it as im sure they are black as night.

I dropped it back down to 75 front / 75 rear...I havent ran it yet, but im getting sick of messing with it......is this a good baseline to go with on this setup? seems like im all over the place and this might be a good 1/2 way point.

Probably not what you want to hear, but I just went through this with my nephews boat.  Stock 454 vortec motor with small marine cam from Comp Cams, 850 Holley DP.  Boat ran good but would burn your eyes if you idled very much. We did the same thing, bigger jet, smaller jet, PV changes on and on but did seem to make much difference overall.   I convinced him to send it to C&J Engineering to have John make it right.  John said the 850 was to much carb on a stock 454.  I found a used 750 vacuum secondary carb and had John go through it.  The boat picked up 800rpm, accelerates hard, plains much quicker, I didn't have a gps, but seat of the pants was probable 5mph faster and it just purrs at idle with no more burning eyes..