As a solo founder for 10+ years, what I can say is that all "rules" in business are "rules of thumb"... Not laws. It's ok to be a solo founder... Sometimes. Bounce ideas off your team instead of your co-founders. Make use of mentors. There is a workaround for all your challenges. I also recommend listening to podcasts with other founders. I host a podcast called "Open Source Underdogs". Lots of good advice there for all founders... Even if you're not working on open source. But there are plenty more. You need outside ideas... Just seek them out.

Don't burn out your friends talking about your startup. It's not that they aren't interested. But nobody needs a single vector relationship.

Also remember that VC's give tons of bad advice to founders. Or rather founders tend to put VC's on a pedestal, and misinterpret what they are saying as advice, when it is really just filter, convenient lies or lazy analysis. Be hugely skeptical of anything VC's tell you, including "you need co-founders".