I am sorry. It was a tough situation that seems to have spiraled out of control. These will do that from time to time, though it makes it no less difficult.
We know your H has some anger issues -- he really, really needs to learn to deal with them.
I can play devil's advocate and tell you how the both of you should have handled the situation. I know, because I and my ex used to do the same things (I can only hope and pray I know better next time.) First, you two should refrain from airing your disagreements before your S's. It would be better for the both of you to show enough respect for each other and present a united front in dealing with a behavioral situation. You should take the differences you have in how to approach the issue with S7 possibly endangering his little brother and hash them out in private. I know that's next to impossible to do in the spur of an immediate crisis -- so it helps to discuss these things ahead of time and to already have an inkling where your partner's mind is on such matters. To be on the same page. But then, this lack of commonality is where the problem arises in the first place, and why such scenes can happen.
It might have been innocent for S7 to play with the scarf with S4, but your H was alarmed -- and he felt like you didn't have his back. Moreover, he felt you were undermining his station and his respect in front of your S's.
And, unfortunately, your H already has anger and self-esteem issues -- and these make for a powder keg waiting to go off.
Unfortunately, it looks like my "post-analysis" is all mute, since the horse is now out of the barn. I hope you two can now use this to get some serious MC. I mean that -- it's long overdue.
Your H certainly needs some IC -- I can see in him the anger I have had to deal with in myself. I know what is like to feel my respect besmirched and disregarded (intentionally in my case) -- it's the last thing in a MR a H wants to lose. Without respect for the H and without love for the W the M cannot long stand -- it takes both to make it work. Respect feeds Love, and vice versa. I pray the both of you seek out counseling -- perhaps this will at last be the catalyst for real progress towards that.
I am sorry for S7 and S4, particularly S7. I really pray it is as I suspect however, that he is just temporarily upset with his father when he says he would prefer you two to split. I want to believe he doesn't really want that.
I honestly don't see anything that can't be mended between you two. It just takes the will and the effort on both your parts. I support you, Irish.