I totally get where you are coming from! Raising my two kids, but especially DS9, is the most challenging thing I have ever done. I can't count how many times I have felt like a failure because of something he did, or how I reacted. Your description of your DS is spot on the same as mine, and no. one. gets. it.
I find focusing on something positive at the end of the day can help, even if it's as small as "he put his dishes on the counter when I asked." Telling him these things ("I really liked how you XYZed today") right before bedtime is good, so he could at least go to bed with a positive message from the day. I also try not to take things personally when DS is being super negative/explosive; this is *really* hard for me, and I'm far from good at emotionally removing myself.
Being new at school can be really stressful, so some of his behavior may be in response to this. I would definitely be talking to his teacher and the principal to work on a positive behavior plan. DS has expressed a lot of sadness and frustration from years of being "the bad kid" in so many classes and groups.
I believe kids do well when they can, so "bad" behavior points to something amiss. The "something amiss" may be the environment (too noisy, bad lighting) or unrealistic expectations (having to be still for too long), not necessarily things your son has control over.
And yes, I sometimes want to run away and hide, too.
