We found the "Transforming the Difficult Child" book mentioned above very helpful.
We initially just implemented the one section where one compliments the child on the large number of things they are doing right and absolutely ignores everything else ("Thank you for closing the door!" "Thank you for using your fork!"). Partly because we couldn't fully agree on the rest initially as my DH and I naturally have different styles of parenting. It may seem like not a very big strategy to just compliment the child and ignore their bad behavior, but this stage took months for us and was extremely difficult.
But doing it helped so much! DS initially (weeks to a couple months) reacted by sometimes doing whatever we complimented him on the opposite on purpose the next time. That was very frustrating to us parents as we then had to ignore the bad behavior (leaving the door open or "forgetting" to use a fork).
DH and I bonded through it, we needed eachother's strength to not react to DS sometimes, we agreed we could grab the other's hand for support and the other would always support or acknowledge them. Both of us would sometimes squeeze the other's hand way too hard as we were so stressed! To this day, two years later, when DS is being particularly annoying we find ourselves grabbing the other's hand and it's still very helpful in making us feel like a team.
Anyways, this is getting long but it did all work in the end, after some months we had a better overall relationship with DS both from his perspective and from ours, the overall tension diminished a bit. Then we were able to come up with a new list of house rules that DS genuinely agreed to and genuinely attempted to follow and which we were more calmly and consistently able to oversee. It included no screaming/loud-yelling (so very loud tantrums then are not allowed and it actually worked!).
The consequence was only a few minute time out. The book suggests the child should see it as just a time to breathe, a little break, but DS always saw it as a punishment, it still worked fine.
One rule we had on the list that reminds me of your DS is "no hurting anyone or anything" because DS would hit himself when upset (threatening suicide is a similarly violent gesture). Luckily the no hitting/hurting rule applies to him also and he therefore stopped. Almost magically, actually, it took only a couple of times pointing that was on the rule list, and receiving a short time out. (But the rules alone wouldn't have worked without the prior many months of establishing a calmer safer relationship with him).
DS is still very much a high strung person prone to drama, to holding onto negatives, not an easygoing person. He will talk about this or that awful thing and it turns out it happened when he was 3. He will perhaps not have an easy life in that regard. But as a family member things are working much better.
