Ahhh I see
that's a lot of time to be putting into each page. I'm still working out my generic manga page style so I can't say how I compare, but I definitely don't take that long to do a page. You can see my non-rendered pages in my last post in my main manga art thread. They took roughly 2.5 hours to get to that stage.
I understand your reasons for practising anatomy at the same time, but I would recommend separating your "practice" from your "actual" work. I mean practice anatomy first on it's own as a warm up or something, do some figure sketches, and then do the manga without putting more detail into the pages than is necessary. Partly because the figures in manga are always partial so you dont get to practice the full body anyway, so it's not too effective.
Honestly I think you're above me in terms of skill so I can't tell what to suggest, other than trying to improve the efficiency of your workflow to improve speed without trying to rush.