It's personal finances, I'm broke. I should leave? But then what, they gave me money and I still own the code. If I took the code it'd be unethical, but I believe in the project and don't want to let it go.
Or just stop working on this and start working on something that makes you actual money until these two are finally ready to make it a 3-person effort.
Yes your time as an engineer is valuable. And your time building that thing was worth taking a risk and learning something, in my opinion. But you don't have a business if you (or they) haven't found users clearly willing to pay.
Even 1/3rd of a good business is a hell of a lot better than 100% of a bad one, or never being able to get anything off the ground at all.
Btw, I know what I'm saying sounds harsh, but I also have to say, mad props for taking this risk. Unfortunately I think it was a bad decision but the experience probably taught you a ton and still cheaper than business school.
"I am out of runway to continue the project. If we want to pitch this I will need a minimum x/per y with a,b,c travel expenses covered when meeting with potential investors.
If they don't have money the project stops. Simple as that. The ownership of the code could be messy, review anything you have signed/agreed to.
I would walk away and start fresh, this is a shit deal for you and if you continue with it, you'll get screwed over more 100%.