On the first point, I've added a small addition to the script to reload MathJax once content changes in-browser, so edits and quick replies should now show you the rendered math once they are submitted.
Looks like they were removed from the toolbar, but I have re-added those for you now. If there are others that are desperately wanted then let me know and I can add those, too.
On mobile, Mark Site as Read is available if you click on the three lines at the top-right corner of the toolbar. This also shows your profile information if you need to edit it. Not sure about the recent activity; can't see an obvious setting for that within the control panel, but perhaps this is just a bug and can be fixed in a later release.