You've only started the car 6 times in the last 2 years? I wonder how the gas is. I learned back in my lawn mowing days to empty the gas tank over winter else a varnish would set up making it hard to start in the spring. I wonder what that old fuel is doing to your injectors.
You said <<every thing from the cap to the plug is almost new>>. But what about between the distributor and the cap. How are the ignition points, condensor and ign rotor. It seems you have a weak spark. If you've not changed the points then check if they need cleaning with an ignition file.
You said <<my 350 does have the std point system with an external resistor coil.>> I already know this. You have a Breaker-Controlled Transistorized Ignition. I know it has points but it also has some other ignition parts you may be overlooking. Are the two resistors (1-2 inches long one is white and the other I recal is blue) on the left inner fender in the engine compartment and the Transistor Switching unit found in the wheel well bypassed? If the system was not bypassed have you tested it to be certain that is not what is causing your poor spark?
If it was bypassed then you may have the wrong replacement coil in addition to your other problem(s). In a bypassed system a different coil is needed then originally called for in your car.
1982 300D Turbo