What about the rest
Not sure. Plane is new to me. I only had it 10 hrs then annual inspection
I agree with the comments on logbook, no way this is 10 hours, looks like the person before you ran it rich and that gap is at least 1 year or a load of flying before you bought it, it may be deceiving but I gather the gap is more than the specs call for.
My thought on this goes back to the original post from full throttle. Check the timing on the mags, clean and gap ALL the spark plugs, I would replace them all to have a clean start and check the wire harness to see that they aren’t rubbed or damaged.
If I was in your situation I would
Check oil- should be tan - not black, if it wasn’t replaced since you bought it, change oil and oil filter, check the oil screen as well.
Spark plugs/ mags next (timing, replace plugs versus gap and clean- to remove any doubt of something being missed- lead can require a pick sometimes and can be missed)
Run the engine through a run-up verify all mags are within range ( rpm or if you have a engine monitor- egts should all rise and all be about the same if one spikes more than others or decreases focus on that specifically. If it happens to be the bottom and the same cylinder the spark plug came out of. Get that resolved, otherwise I expect it will all be good for a flight.
After 10 hours if all seems fine, check that spark plug again.
That’s what I would do, but you have great feedback on other options.
Please let us know how this works out.