I recently worked on a project similar to this. Based on my experience, these are the things you need to do:
- Take a break for 3 days minimum. Go cold turkey, preferably not in the same city you are in. Just get out of there. It'll feel crazy, like you don't have the time, but trust me: at this point you're endangering your own health and the project. If you're a single point of failure, and it sounds like you are, things could go very pear-shaped if you keep this up and really fry your noggin. Which leads to my next point;
- You need help. You're trying to do too much, and it's just not possible within your apparent timeframe. See if you can get someone else in to help, or get one of the other team members to pick up some slack. It's completely unfair to expect 7 x 10 hour days from you, and anything less from the others. I'd state your reasoning calmly and clearly (after you've had a break; use the time to reflect on your work and where the project is going, trust me it will look different), and let the team know it's just not feasible unless you come back at significantly reduced hours + extended timeframe, or get some else on + extended timeframe to bring them up to speed. These are the realities of where you are, and the sooner you fess up to them (to yourself, and the team), the more chance you will have of salvaging what you've got.
- Take a break for 3 days minimum. Go cold turkey, preferably not in the same city you are in. Just get out of there. It'll feel crazy, like you don't have the time, but trust me: at this point you're endangering your own health and the project. If you're a single point of failure, and it sounds like you are, things could go very pear-shaped if you keep this up and really fry your noggin. Which leads to my next point;
- You need help. You're trying to do too much, and it's just not possible within your apparent timeframe. See if you can get someone else in to help, or get one of the other team members to pick up some slack. It's completely unfair to expect 7 x 10 hour days from you, and anything less from the others. I'd state your reasoning calmly and clearly (after you've had a break; use the time to reflect on your work and where the project is going, trust me it will look different), and let the team know it's just not feasible unless you come back at significantly reduced hours + extended timeframe, or get some else on + extended timeframe to bring them up to speed. These are the realities of where you are, and the sooner you fess up to them (to yourself, and the team), the more chance you will have of salvaging what you've got.
Just my 2c.