Yeah it sounds like a boot problem if it's new plug with the same problem.
Curious about how difficult to start? Seems like a strange way for the spark to travel being that you said it runs, meaning it's sparking in the area it is supposed to. Makes me wonder if you have a bad ground from the head, if the spark is indeed happening at the tip of the plug as intended (if it's going from the boot around the outside of the spark plug then it would ground out at the head and not run) then the return path is the part that is to blame, especially if you kill the motor by touching the plug or boot since you changed the return path to ground.
You have a painted motor head by chance? If you have a multimeter try checking the resistance of the motor by putting a probe on the head, and the other on something like an exhaust stud, if you don't get a reading then you don't have a solid ground. If you do get a reading then you might have a really weird wire problem or for all you know a second defective plug.
Just seems so odd for the spark to jump the air gap on the outside of the plug but also successfully spark in the combustion chamber..