I'll try some suggestions.
Use an ohmmeter, measure all the spark plug wires for resistance. They typically will be in the 3,000 to 6,000 ohm range.
What ignition system do you have? Make sure all the connections are clean, and, if it is the stock Mopar ignition module, make sure the case is well grounded to the chassis.
Your 18" of idle vacuum in neutral seems pretty good. The idel variations look normal for a small misfire, and not of any sort of valve problem.
I notice that you said that the engine wanted to die if you started to cover the carburetor. This indicates that the mixture is rich. I would suggest that you lean the mixture and ignore the vacuum gauge readings while doing that. Then try enriching the mixture, again ignoring the vacuum gauge.
Please take out all of the spark plugs and post a picture.
Look down into the carburetor while idling (a mirror and flashlight is useful for this) and make sure there are no visible drops of fuel going down into the carburetor.
And your English is very good!