B&M Converter is bad

OK slot is all set and distributor back into the car. I started at 8* btdc. Set idle to 800, and adjusted the carb. I was originally pulling around 10 on the vacuum at 1.5 turns out. Started unscrewing the screws equally out and got up to 13-14. Readjusted the idle and then reved it up to about 3k. I was only at about 30*.

I retimed to about 13* ran thru all those steps and was closer to 38*. Hooked advance up, Got in the car and put it into gear and it dropped about 300rpm. Shut car off and it chugged and backfired thru the carb. So I re did everything at 10* initial. Reset everything and was about 34* total. But now I'm dropping about 4-500 rpm in gear and its not liking it.

Couple questions. I'm not totally sure my idle screws are working properly. I have the left screw out 3.5 turns and the right 3.25 turns. Only able to pull 13-14 vac. Is it normal to have them turned out that far? If I'm backfiring thru the carb do I want to advance it or retard it? If I retard it I'm getting further away from the 34-38* range? Is that Ok, is there a point that is to low?