I hear you on not having time for PTs. Something that will help would be getting protein-rich conditioners as an RO and even leave-in. If you check the "protein-craving" section, there's a good thread on protein-rich conditioners. Try NG Biotin, Millcreek Keratin (strong) or Biotin, EO Keratin, Giovanni SaS, none of these have polyquats. People really like CJ Repair Me, I think I could use it as an RO.
Yes I think you should sulfate wash to reset everything while moving forward. You can use the GVP CB + coconut oil + honey to DT afterward to put back moisture... or just leave the GVP CB longer in your hair in the shower.
Yes I think cowashing could be contributing to overmoisturizing issues... you can either cowash but cut back on the moisturizing RO and/or leave-in, or switch to regular low-pooing and keep the moisturizing (and protein-ing) RO and leave-in. The thing is if you cut back on RO and LI, but keep cowashing, you won't really be getting your regular protein fix, so yeah I guess I'd recommend low-pooing more regularly.
Everything in my siggy is polyquat-free. Look at kathymack
's siggy and ask her for recs too! She has your properties. I'd highly recommend you try homemade flaxseed gel if you haven't already.