But a good sounding board can help you hammer out why things aren't working and what might be done about them. They won't make your decisions for you nor tell you what to do. A good sounding board listens a lot and comments a little and makes thought provoking comments. They do a bit of reframing. They give you some perspective.
It can be a huge sanity saver to have a good sounding board to run things past. This is much, much, much more valuable than a psychologist or crying on the shoulder of a friend or loved one. Sometimes friends or loved ones can play the role of sounding board, but that isn't guaranteed.
I don't know how you can find a good sounding board. But I think this would do more for you than talking just to vent about the stress. I agree that you need very much to talk with someone, but not just to blow off steam. You need to be able to go "AAAARGH!!!! The Whatsit is NOT fucking working AGAIN for the third fucking time this fucking week" and have someone say "So, with that much downtime, would it make sense to buy a second Whatsit? Would having two of them eliminate one of the major sources of stress in your life?" or even "So, explain to me what a Whatsit does. Why is this such an enormous source of stress for you?" and then in the course of explaining its role in the business, you have some epiphany about how things work and why you keep tripping over X, Y and Z issues.