This may not be helpful, and I'm not an expert, but I really don't think anyone should wash the full length of their hair multiple times while in a protective style. That's not something I'd expect to be able to do. I'll admit, I've only discovered the issue from trying to wash marley and mini twists while keeping them in for more than 3 weeks. My hair was matted and I tore out some of my mini twists, because they were locking. I think if your hair is like mine, short term protective styles that take less time to install, make more sense. Take them down to wash your hair.
I've made posts about my hair webbing, tangling and not being easy to part, but I think that washing once a week, so I can fully detangle and remove shed hair, using a comb instead of finger detangling, and only styling while wet seems to be helping me.
Also, I probably have SSKs on the ends of 80% percent of my hair. I know they're bad, but I don't think it's a huge deal.
Maybe you already tried everything, but I just thought I'd put my two cents in, since I have similar issues.