Back to your "how many wedges" question...2 steel wedges will be fine. But bring 4 wooden wedges along to act as followers. Use the steel wedges on the leading edge of the split and leapfrog them. But then feel free to use the wooden wedges following up behind to help keep things moving along. Even a soft pine wedge from a 2x4 can help, though hickory, ash, maple, osage etc will give you more usage.
Good luck, you got this far and there is no sense not splitting things out and getting on with the wait and cure process. If it turns out to be something other than what you want, so what? Make bows, not excuses!