Thankfully the ignition is pretty sturdy on these things. The potential to damage the ignition is greatest when turning it over with power to the ignition on and NO spark plug installed. The spark that's created in that situation has nowhere to go, and it's strong enough to use it's imagination finding a place to ground. Unfortunately, that's often through the pick up/sensor, whose components are not rated to handle that kind of power, making it kind of a weak spot. Generally those are pass fail, so I doubt seriously yours is damaged or causing your problem.

If the plug is inserted in the boot correctly, the metal boot and braided wire attached to it act as a ground (all you need). You do NOT need to touch the plug to the cylinder for a ground.

As far as restrictions, your engine is idling well, and seems OK at wide open. For me anyway, I struggle with the idea of there being a restriction.

Wing on the airplane only to minimize the fuselage dancing around, especially while on idle. The wings dampen that rocking motion caused by the single cylinder engine.

If you haven't done it yet, you need to establish a base tune (procedure to do that described in my last post) prior to any further "tuning". Reason being, you need to get the fuel flow balanced between the low and high speed circuits. You want the high speed circuit supplying the majority of the fuel when running wide open, and the idle system supplying the fuel on idle. The ONLY way you can do that is to establish a base tune. If this seems contrary to your thought process, there's another totally different way to adjust the carb that uses completely different logic. It no easier by any imagination, and it does not change the end result. It still requires the engine to be run at wide open throttle as part of the process. If you'd like to know more about it, send me your email via PM. This site will not allow us to post links to other sites, even via PM. -Al