Since you've checked you points and condensor...by default you have a non electronic ignition and therefore most assuredly should have a ballast resistor. (the rectangular dodad from the above photo). Also, it wouldn't hurt to put in yet another new condensor...I've had them bad right out of the...
Oh, almost forgot...so it sounds like you don't want your weber anymore....for the right price I'll take it off your hands. ;) Send me an email if you want to sell it.
If after you done the above for vacuum leaks and checking the points.....and if it is still popping and spitting (non electronic ign only here) (and also rule out any issues with the dist cap arcing) put in a new condensor. When condensors go it will cause backfiring and spitting. Next stop...