The conclusion I've come to is that you're overreacting. You've gotten a lot of options on this thread. I'll add one more, listing it first. Pick one or more and do them.
* Hire another product lead to manage the front-end of the project.
* Convince your partner it's time to seek outside funding to scale the business.
* Hire a VP/Marketing, VP/Engineering, or VP/Sales to add a stakeholder who will be objective and put pressure on your team not to make dumb decisions.
* Convince your partner to add a minority partner, splitting the equity cost equally between the two of you, so that you can have another person who is fully focused on the business (and, don't say this to your partner, to break ties).
* Hire a mediator to hear you and your partner out and agree beforehand that you're going to abide by their decisions.
* Wait it out. For ~3 years or so your partner managed the business, kept things organized, got people paid, did sales at least as well as you did, and generally made up for all the gaps you (like everyone else) had. When things calm down with his personal life, maybe everything will be fine again.
* Hire another product lead to manage the front-end of the project.
* Convince your partner it's time to seek outside funding to scale the business.
* Hire a VP/Marketing, VP/Engineering, or VP/Sales to add a stakeholder who will be objective and put pressure on your team not to make dumb decisions.
* Convince your partner to add a minority partner, splitting the equity cost equally between the two of you, so that you can have another person who is fully focused on the business (and, don't say this to your partner, to break ties).
* Hire a mediator to hear you and your partner out and agree beforehand that you're going to abide by their decisions.
* Wait it out. For ~3 years or so your partner managed the business, kept things organized, got people paid, did sales at least as well as you did, and generally made up for all the gaps you (like everyone else) had. When things calm down with his personal life, maybe everything will be fine again.