Car engines are harder to tune because the only way to tune for higher revs under load is by driving them. Assuming the plug and fuel are good, open the high speed needle to a quite rich setting (or what you'd consider to be very rich). This ensures that at idle then only the idle needle will be controlling the fuel. Start the engine and slowly lean out the idle mix after it's warmed up for a few seconds. If the revs start to drop you'll know it's too lean so go the other way. If the revs start to rise as you lean it then you'll know it was too rich so keep going until the revs begin to drop then richen it back up a little. That'll give a reasonably accurate idle setting.

Now you'll have to drive it to get some load on the engine when you open the throttle. Open the throttle very slowly and listen to the engine and also watch for smoke from the exhaust. Ideally the engine should be running quite rich when the throttle is opened enough for the high speed needle to come into play (roughly around half throttle). If it sounds like it's 4 stroking with lots of smoke then it's rich so bring it back and lean the high speed needle a little and try again. For running in, the mixture you want at full throttle is where it's just barely got into a clean 2 stroke but a bit of 4 stroking sound is fine. At this stage you're not looking for instant acceleration from idle, that can come later after the engine is run in, so give fairly slow movement on the throttle.

If this still doesn't work for you then it's likely to be either a bad plug or bad fuel, maybe even both. Given the problems you're having I'd be inclined to fit a new plug first (preferably a hot plug) and then get or borrow some fresh fuel to try.