The built-in WordPress commenting system.
Not at this time.
Yes, see documentation on notifications.
See Loco’s documentation on how to save translation files safely.
Not in Directories Pro currently, but they plan to add Leaflet.js support which will avoid the necessity of the API.
Directories Pro should work with almost any theme.
Directories Pro should work with any user management plugin, including Ultimate Membership Pro.
There is no way to add a profile tab to the BuddyPress page like there is in Sabai Directory, but it is planned for a future version. One can integrate with the activity stream in BuddyPress using BP’s own functionality.