I do not see how you could possibly drill the hole without having aluminum shavings falling into the combustion chamber. that is why I suggested taking out the head. Even one very small shaving could possibly do two things. First it could get stuck between the valve seat and the valve head and not allow the valve to close completely. This could leave the valve protruding out of its position and consequently getting hit by the upward movement of the piston resulting in more damage. Secondly it could simply short out the spark plug which would mean no spark and consequent engine vibration. Lets hope that this is what happened. Also if that is what happened then the air/fuel mixture would not ignite but instead would pass out from the exhaust unburned hence the smell of gasoline (by the way, unburned gasoline passing through the cat will eventually damage it). I suggest you take the spark plug out and check it. If it is fine then go ahead and do a compression check on the engine.
Another very gross backyard mechanic way to clean any shavings from the combustion chamber would be to remove all the plugs (which you would be doing for a compression check anyway) and crank the engine to hopefully spit out any shavings if they are still there and loose (doubtful).
One thing I did not understand from your second posting is that the #1 plug got thrown out. Is this the plug you fixed with the helicoil, or is it another plug?
Also, the smell of gas can simply be a result of the fuel mixture coming out of the #1 combustion chamber since there is no spark plug.