I have talked with the team, and we seem to all understand that this is not going the way we want. I have made it clear that I will be looking for others to join in a "co-founder" capacity if I get the opportunity to go to YC this winter. They are reasonable people and good friends, so I don't think it will be a big problem to do a little equity restructuring if its in the best interest of the startup.
My real question is not "am I screwed?" because I already know that. I'm asking "how can I fix this now?" or, in other words "please help me find a new co-founder and a chance to get into YC (or another good startuppy environment)."
I can't really help find a new cofounder (other than reiterate what others have said: ask around here, check cofoundr.com, etc.), but I can tell you what we did. We (my surviving cofounder and I) bought out the other 3 founders for $1000 apiece. In retrospect this was probably too high, given how quickly they accepted. But it was done mostly to preserve good relations and make sure nobody felt they were being cheated, and I think it succeeded in that. When our incorporation papers come through there will be a few agreements for them to sign to make sure we own the stuff they did before we bought them out.
"The number one thing not to do is other things. If you find yourself saying a sentence that ends with "but we're going to keep working on the startup," you are in big trouble. Bob's going to grad school, but we're going to keep working on the startup. We're moving back to Minnesota, but we're going to keep working on the startup. We're taking on some consulting projects, but we're going to keep working on the startup. You may as well just translate these to "we're giving up on the startup, but we're not willing to admit that to ourselves," because that's what it means most of the time."
I've run into similar situations before. This is a serious problem and one you should deal with immediately, because it will only get worse. Have an honest, tough talk with your team. It sounds like you won't convince them to put it all on the line like you have, but at least you'll know and you can make an arrangement so that you're moving forward with the company and not having this looming over your head. If worse comes to worst, tell them you are going to move on because its sounds like you are pretty talented and there are many opportunities for someone like you.
Good luck.