No worries!
I think in general, being conservative with attachments is good. I usually start by just doing the origin and insertions, and getting as far as I can with those + fibers + inertial damping + collisions. From there if the performance still isn't right, I'll start adding selective muscle-muscle and muscle-bone attachments. These are typically quite a bit weaker than the origin/insertion attachments.
As for your fascia losing detail. You have an attachment from the fascia (all vertices) to the fat right? That attachment should be quite stiff. Maybe 1x108. And contact stiffness on all the zBones and the zTissue can be a bit higher now because you're colliding with tissue. So something like 1x107.
What is the point count for the fascia? I think for your character something like 25k vertices with nice evenly spaced quads should be enough detail 🙂
Have sent the scene back just now