Ask HN: How to navigate co-founder model with ambiguous roles?

It's an early stage bootstrapped startup with two co-founders and an advisor (48/48/4 split). I met the co-founder through work, we worked together for nearly 1.5 years before he was laid-off. We both come from technical background, and have both good experience in building 0 to 1 products.

I had always talked about how I want to start my own startup. After layoffs we were casually talking, and about a month ago we decided to start exploring what we could do.

Initially we explored couple of ideas in industries which both of us were somewhat familiar with. But nothing really stuck. Co-founder found this niche in healthcare which seems promising, so we decided to explore further. Since neither of us were SMEs, we agreed to set aside 4% equity for an advisor (contingent on revenue goals), who can help us gain more exposure & industry contacts.

Since the co-founder is more familiar with the industry (it was their minor during college) and has free 9-5, he took the lead on discovery work around user interviews. Since I'm good with arts & tech, I helped with some creative stuff and setting up some dev basics. I'm good at finance stuff, so I took a lead on creating a cap table and accounting spreadsheets.

Recently we experienced some friction, mostly because I felt a certain lack of collaboration. We never really discussed the insights from user interviews or path ahead. Co-founder started writing down PRD and designing wireframes. Some of the scheduled interviews were flaky, which frustrated the co-founder, so he decided to cancel them and decided he has enough information to move forward.

Again, I don't know much about the industry, I am still trying to catch up on industry jargon and understanding the problem space. To my co-founder the problem space is very obvious to get started. I have lot of questions about the vision, the product, the approach etc. If he had product or design experience, maybe I would have more faith. In past he has mocked PMs couple of times (jokingly). I critiqued wireframes he shared, which he brushed off saying these are very early stage and I don't understand design process. I asked how come these wireframes had so much styling if they were early wireframes. He replied, it can't be helped if they become high fidelity more he organizes the diagrams.

Co-founder blames this on me having a 9-5 as he has more time to explore and move fast. But that seems tad unfair because I try to set aside weekends and 5-9 to this venture, while he's only available 9-5 on weekdays.

My first question is, should I keep letting him forge ahead while I lack clarity around vision & product decisions?

My second question is, how should I set & enforce boundaries around finances? Till now he hasn't spent that much money but there's been no discussion on any of the expenses. I'm concerned that if we get credit cards, I might just end up seeing larger line items we never talked about.