Help with tuning issues

Hello everyone, wel here is my dillemma I bought my 71 malibu with a fresh motor, however I have had to hook the transmission vacuum line and the distributor advance line to it. The car was way advanced when I got it so I set it to 8 degrees, it seemed to run smoother at low rpm so I went one step forwar and changed my plugs gapping them to 45 as directed by the parts store or ac delco, this is where it sarted getting worse, I am getting 13 inches of vacuum steady which is saying intake leakage or vacuum leak, neither of these seem to be happening it seems like an ignition problem, it runs smooth at low rpms and when I accelerate a little further it misses but then catches itself, my next step is to change wires. Also I noticed today when I looked inside my carb the the jet was only shooting on one side, but it looke like it was in the middle of the carb, it is a holley 600 cfm electric choke 4 barrel part #80457. Anyway here is where I am also the car had a bit of an rumble and supposedly it has a mild cam but I dont know because the car runs pretty bad. Any help would be appreciated. I am new to carbureted cars and looking to learn and make my car run optimum. Thanks