You are taking too long to build an MVP, specially the amount of work you are putting on it. Dont be a feature creep, focus on what is essential and show it to your users. Even if you finish your MVP, it could still a long way to start having revenue, imagine profit or being able to get funded.
Ideally you should have an income or savings even if your startup makes money, taking a salary could hinder other sector of your business.
And your cofounders should know about your situation, because if you put yourself under financial stress, it soon will reflect on you job, so be honest with them.
What about a half period or weekend job, is it enough to cover your expenses?
I am an electrician and I charge 10% to buy components, but I do not specify it to the customer, because most complain about.
Best way to find your price is knowing your total costs first, and how much is per hour. Then pretend to be a customer and ask for price estimative from competition.
After this you need to have a better price then the rest or a better service/differential to charge more then your competition.
Check at Fiverr and Upwork to see also how much the sellers charge fro similar services, or local association. Usually they have a base for price per service.