It's probably closer to 5000 ohms/ft, but it doesn't really matter. If you have continuity, the wire is almost certainly OK. There is no mechanism by which the resistance would double, and even then, it probably wouldn't cause a misfire. Better to try flexing the ends where the connections are made and see if the cable open-circuits. Also, take a good look at the connections to the cap and plugs and make sure they fit tightly and solidly. I'd look for the usual, banal causes: cracked cap or rotor, fouled plugs, that kind of thing.
Are you sure the problem is in the ignition, and not carbs, fuel delivery or some such thing?