just had the same prob with mine. If you have tried a rattle gun and it doesnt work get a big breaker bar and socket, park the car on the concrete, disconnect the coil lead and crank the engine a little bit at a time (better if there is 2 people so one can keep any eye on the bar while the other one cranks it). Mine came loose after about 7 cranks
If you already have the bolt out but cant get the balancer off go and buy a balancer puller they start from about $18 for a supercheap one but most dont come with the correct bolts for the balancer so just go to a nut and bolt place with a bolt that does fit and ask for some high tensile ones