Another quick check is pull each plug wire while running to make sure every cylinder is firing. I had an early f engine run on 3 cylinders and it idled fine, but would not take any load dor obvious reasons!
Give it more advance, sounds like retarded timing, dont be afraid to go 15 degrees. If its too advanced it will not start easily. The bb is not always accurate. Hate to admit it but I time these by ear, test and tune, drivability, make sure its not detonating etc.