Great update, lot of nice stuff happening.
Couple of things.
What is the latissimus attached to, in your setup? it doesn't look like it's extending/contracting with each step. It should be low enough down the humerus to get pulled forward each time that leg extends, and then should get pulled tight with a line of action feeding into a zfiber, when the leg comes back.
Looks like the sartorius is buckling/pulling away from the other muscles in the upper leg. It could be that the attachments aren't configured quite right. Could be that you need a fiber contracting when the knee lifts up.
I like the movement on the brachiocephalicus though, this is a key one to get right on quadrupeds. Seems like the muscles have a nice weight overall.
Right, on to the fascia. Nicely modeled, good vertex count for a creature of this complexity.
The thing is, it's looking quite pinned. The workflow you're going with was one that I used in the early days on the lion (and chenchen did on the horse) long before our cloth model became the stable beast that it is today.
What I would do, is just delete all the attachments going to the fascia. Except for some fixed attachments on the border vertices so that it doesn't ride up during simulation.
Use rest scale / pressure + collisions to keep the fascia tight onto the underlying objects. It will make the results look much more organic.
Once you have that, you can selectively add fixed/sliding attachments to tune the performance how you like it.