I like a lot of what you are doing, and I might donate your cause, but I feel there are some questions that need to be asked. (I feel uncomfortable about the questions, that's why I use a pseudonym.)
Have you considered cutting salaries in half? According to the table you share in the comments, you spend 1.4 million on the salary for the 6 of you, which is $230k per person. If the org was in a better shape, I would consider this a reasonable salary, but I feel that if I was in the situation you guys are in, I would request my salary to be at least halved.
Relatedly, I don't know if it's possible for you to run with fewer employees than you currently have. I can imagine that 6 people is the minimum that is necessary to run this org, but I had the impression that at least one of you is working on creating new rationality and cognitive trainings, which might be nice in the long-term (though I'm pretty skeptical of the project altogether), but I would guess you don't have the slack for this kind of thing now if you are struggling for survival.
On the other side of the coin, can you extract more money out of your customers? The negotiation strategy you describe in the post (50-50ing the surplus) is very nice and gentlemanly, and makes sense if you are both making profit. But if there is a real chance of Lightcone going bankrupt and needing to sell Lighthaven, then your regular customers would need to fall back to their second best option, losing all their surplus. So I think in this situation it would be reasonable to try to charge your regular costumers practically the maximum they are willing to pay.
Thanks for the answers. I appreciate the team's sacrifices and will probably donate some good money to Lightcone.