I'm about to give up

I fell foul of the oddly arbitrary spam filter earlier so it's possible this reply will also get eaten and be released later but here goes:

First of all I wanna say you are so strong going on as long as you have and I'm glad you didn't give up or end things, please put something in place so you can also take care of yourself, the strong might not quit, but they definitely need  to take breaks from time to time.

Secondly I'm not going to pretend to know EXACTLY what to do, I'm not in your shoes, I don't live with you, and even though you listed some really key information here I'm sure it is only a fraction of a fraction of what is really going on on the other end of this wifi connection. So the only practical advice I can give you as someone whose autism seemed to go through a worse patch at one point is that when the underlying cause is resolved the external way it is expressed through behaviour gets better. It sounds like you really need to get to the bottom of what A started it, and B what is "holding the gas pedal down" on it when on the surface it looks like it has been dealt with.
If you are tiptoeing around trying to avoid triggers that might not be the best IF (and I do say IF) the original trigger was a traumatic experience linking the stimuli to become associate with a strong negative emotion, like feeling out of control, fear, intense physical discomfort, etc, because IF it is a trauma response the fix may need to to look more like treatment for PTSD than just direct autism sensory avoidance. Have you tried minimal controlled exposure to the triggers where everyone remains calm and the thing immediately stops and becomes a non issue because it gets treated as a non issue?
This is not going to be the exact same but I have to share it to prove a point about how trauma can look through an autistic lens. But the reason I ask is I noticed my own child (I'm autistic and he is awaiting assessment) at age 3-4 saw someone else have an adverse reaction to dogs and modelled the behaviour, flinching and screaming whenever he'd see a dog despite never having his own directly traumatic experience with one, in the end we had to do a very slow paced exposure therapy to get to the point where he can have one around him without physically flinching to get away. And it has taken 6 years to get him to the point that be can tentatively and then ease into patting a dog on the head. It is a very long healing process so IF it is trauma related the sooner you can narrow down the origin and the mechanism of it the sooner treatment can begin. Especially because the treatment must be adjusted to autistic sensitivities and a more paced out time freame so as not to risk everyone burning out. I also mention it because if your son can sense you getting upset when a trauma trigger happens that might be reinforcing the idea in his head that yes this must be the appropriate response because it upsets everyone else too. It can be very tough but in those moments of crisis you need to be the serene and calm one, stead,y unchanging, safe and reliable, setting an example, even if it's just "see? it can't hurt you. something bad might have happened with it before, but that doesn't mean the bad thing is always going to happen." But again that's really my experience of an autistic trauma response.
I really don't expect you to take my word for it alone and really advise you seek guidance on trauma from a childrens PTSD specialist.

I fell foul of the oddly arbitrary spam filter earlier so it's possible this reply will also get eaten and be released later but here goes:

First of all I wanna say you are so strong going on as long as you have and I'm glad you didn't give up or end things, please put something in place so you can also take care of yourself, the strong might not quit, but they definitely need  to take breaks from time to time.

Secondly I'm not going to pretend to know EXACTLY what to do, I'm not in your shoes, I don't live with you, and even though you listed some really key information here I'm sure it is only a fraction of a fraction of what is really going on on the other end of this wifi connection. So the only practical advice I can give you as someone whose autism seemed to go through a worse patch at one point is that when the underlying cause is resolved the external way it is expressed through behaviour gets better. It sounds like you really need to get to the bottom of what A started it, and B what is "holding the gas pedal down" on it when on the surface it looks like it has been dealt with.
If you are tiptoeing around trying to avoid triggers that might not be the best IF (and I do say IF) the original trigger was a traumatic experience linking the stimuli to become associate with a strong negative emotion, like feeling out of control, fear, intense physical discomfort, etc, because IF it is a trauma response the fix may need to to look more like treatment for PTSD than just direct autism sensory avoidance. Have you tried minimal controlled exposure to the triggers where everyone remains calm and the thing immediately stops and becomes a non issue because it gets treated as a non issue?
This is not going to be the exact same but I have to share it to prove a point about how trauma can look through an autistic lens. But the reason I ask is I noticed my own child (I'm autistic and he is awaiting assessment) at age 3-4 saw someone else have an adverse reaction to dogs and modelled the behaviour, flinching and screaming whenever he'd see a dog despite never having his own directly traumatic experience with one, in the end we had to do a very slow paced exposure therapy to get to the point where he can have one around him without physically flinching to get away. And it has taken 6 years to get him to the point that be can tentatively and then ease into patting a dog on the head. It is a very long healing process so IF it is trauma related the sooner you can narrow down the origin and the mechanism of it the sooner treatment can begin. Especially because the treatment must be adjusted to autistic sensitivities and a more paced out time freame so as not to risk everyone burning out. I also mention it because if your son can sense you getting upset when a trauma trigger happens that might be reinforcing the idea in his head that yes this must be the appropriate response because it upsets everyone else too. It can be very tough but in those moments of crisis you need to be the serene and calm one, stead,y unchanging, safe and reliable, setting an example, even if it's just "see? it can't hurt you. something bad might have happened with it before, but that doesn't mean the bad thing is always going to happen." But again that's really my experience of an autistic trauma response.
I really don't expect you to take my word for it alone and really advise you seek guidance on trauma from a childrens PTSD specialist.

And I second what Shardovan said, if you get to the breaking point again reach out to someone, you deserve to be heard and take care of yourself too.