Start by soaking the crank snout a day or two with a good penetrating oil. Kroil, PBblaster are two of the best and usually available locally. You can probably get the bolt out with a left hand drill bit.
When you're ready to try again, use anti-sieze on the bolt and balancer threads. If you break another bolt, the anti-sieze will make it easier to remove. And the balancer threads will load more uniformly. Use grade 8 bolts, be sure they are screwed in evenly so the load is distributed. If you have a strong U.S. made puller, use an impact wrench. If no impact, smack the end of the puller with a 3 lb. hammer when it is down tight.
As stated, use heat only if you have to. Too much will cook the rubber inside the dampner. There's a fine line as to how much heat is too much.
I've been using a good puller since high school, seems like it's 100 years old.
With grade 8 bolts, I haven't broken any bolts, but did pull the threads out on one. Went to a bigger bolt and it came right off. But now I have probably jinxed myself.
