You need to knock this on the head once and for all.
Otherwise it's going to build itself into your relationship dynamic permanently, and chip away at the love and respect.
Sit him down and tell him that unless he gets a grip and stops with this behaviour, your relationship will fail. Maybe not right now, but you won't go the distance.
Tell him this has nothing to do with your friend, and when you eventually leave him because of this issue, your friend will be the last thing on your mind.
Make it CLEAR that you will not stay with a husband who makes your life a misery with his jealousy. A husband who doesn't respect you enough to assume you will be faithful. Who makes it clear he thinks, deep down, that you are nothing better than a slut (yes, use that word. Give him a shock - this IS essentially what his behaviour is saying to you). That you won't have your children learn from a nasty, suspicious, sniping, mean-spirited father and eventually you would make the decision to protect them from that attitude.
Scare the bejesus out of him with a clear picture of what the future holds unless he GROWS THE FUCK UP.
Tell him that as you don't think he's man enough to get help for this, you're warning him now that the other option -splitting- is looking more and more likely.
Then sit back and say - that is your warning. It's up to you what you do.