This is looking awesome!! Only a month's work? Great stuff
Some questions / comments --
Sounds like you're driving the fascia correctly to me. (combining muscles/bones into a single mesh and exporting to Alembic)
So when you say you didn't drive the muscle excitation, did you just have a constant value across the whole animation? Or is it that you're not firing them at all, yet.
How do the intersections between objects look at default? Are you using collisions?
We've been finding lower resolution fascias have been more successful. Are you able to post more stuff about your fascia?