My SO is undiagnosed and I don't believe I can do this alone... .Is it wrong or has anyone done an intervention where family and close friends are brought in to support and help him understand his condition? I don't know if I can remain in this marriage if he does not get help. I do all I can to be responsible in my actions and reactions to him but I'm crushing under the pressure.

No, it is not wrong to want it. I can understand needing support of others. You don't have to do this alone, the folks here are a great resource as a place to learn skills, vent and truly help the relationship be a little more balanced than what it may currently be. Check out all the tools on the staying board even if you are undecided about the marriage. Using the tools will help the conflict.
However, that is not really the best course of action if you want true change. The fact is BPD is truly a mental illness, having friends or family involved will make your pwBPD feel alienated and likely not yield the results you with to have.
So, what can you do? Get some information to help you cope - most definitely.
Does your H acknowledge the relationship itself (not just him) is a problem or high in conflict?