I was also using a crowbar just after the puddle to keep the slag from rewelding itself back together.

No. You need to adjust the torch so that it blows the slag away. If you are getting lots of slag you are a) not at a correct angle b) not enough pressure on the O2 for cutting. There are a few more explanations, but if you can set it to cut smoothly, without much slag, then it is correct.

Am I on the right track or is the torch not the preferred tool for this job?

Personally, I would use the cutoff wheel more, followed by the grinding wheel. Cutoff as much as you can. Don't try to break the bead with the cutoff, but instead, remove the bulk of what you can and then grind the rest of it out of your way.

But that is me. I find the torch a PITA in close quarters. Semi-messy with too much else to catch fire that you don't want to catch fire.

Also noticed I can barely cut through the front lower a-arm mount with the torch is that because it is cast?

Yes.

Good Luck,
Michael