1) You can add pages. The menu should not disappear. Contact us know if this happens.
2) I can’t log in. Have you changed access?
3) Theme Options > Typography > Menu > Menu 1 level > Font Color.
4) “Double menu” header type has 2 menus. You can mark any menu as “Left menu” or “Right menu” https://prnt.sc/mk2kxw In case, you will change header type in Theme Options > Header > Header layout, only one menu, marked as Left, will be shown.
Regards