Thanks for the suggestions. Finally a buddy of mine and I were able to get the damn sprocket off last night.
The jaw puller would only hook around the front rim and very neatly pulled it right off the sprocket. I should have gotten a puller with skinnier arms in order to have it hook around the back of the sprocket. The one I got was heavy duty and the arms were too thick.
The heat gun followed by much hammering on a spare set of wrenches I had laying around were able to finally get it off. Thankfully I don't need to reuse the old sprocket since it got pretty banged up in the process. Also bent a few wrenches but who cares.
Now the machine runs up to 2400 rph with the new sprocket. As of yet no weird noises coming from the gear box or motor, so hopefully nothing was damaged by all the hammering.