I'm sure it's not recommended but I crack the inlet hose to the regulator just very briefly and look for a small squirt of liquid LPG. If that's ok I test the primary pressure, the 1/8 brass pipe plug on the front of the regulator. If I remember right you're looking for 1 to 3 psi. Automotive vacuum gauges often have a pressure side that will read that low. I'm surprised you found a regulator with a button. All the replacements I've seen for the last decade have been the Cobra model. (which is recommended)

Also make sure all your vacuum lines are connected. Another thing, running too rich will give you the same symptoms, only difference is you'll probably smell the LP. I wouldn't mess with the distributor because it runs well on sprayed fuel.