I went through all the same things when I first got my '48 running. My biggest problem (and probably the most obvious) was that I thought I had my points adjusted correctly, but I must have bumped something or moved them when I tightened them down and they were just ever so slightly open when they should've been closed.
1.dump the 12v coil/resistor for a 6v coil
2.check/replace spark plugs
3.check/replace cap,rotor,condenser
4.check/replace plug/coil wires
5.file and re-gap points
6.check, re-check, re-re-check firing order and
distributor position at TDC
7.remove,clean,reattatch every MAJOR electrical
connection. (batt., frame, engine ground,
starter, coil, dist.) leave no doubt that you
have all good connections!
8.check compression
9.check for adequate fuel supply
That should be your basic list of requirements to get an engine running. I have to believe that the external resistor is getting in the way since you mentioned a weak spark.
Remember, when these stovebolts are set-up properly, they usually only take a couple revolutions to come to life. Should be no need to crank the heck out of it. How else would you be able to start 'em with a hand crank?
