You sound like a wonderful parent and also exhausted from trying to do everything right. When my son was 5, he seemed almost to need a daily tantrum to regulate himself. I found some of the tips from hand in hand parenting to be really helpful. The parent support groups were such a relief. I switched to just listening to his tantrums and saying things like I am sorry this is so hard. And telling myself that he would be happier once the tantrum was over. And he was sweet and easy for the next or two until the next one. Patty Wipfler is the head of the organization and has a wealth of written materials that I found helpful.
It is so hard to be a good mom, especially if a child that needs extra attention. I hope you find time to take care of you too.