Is there a (video) tutorial or similar?
No.
It is planned to provide some video tutorials, but this service will not be free ...
Q1) I work on international projects, many have standard working weeks Sunday - Thursday. How can I best change the default calendar settings i.e. To Fri/Sat non working or remove?
On the calendar, click all fridays (they will become closed days) and click and click all sunday (they will become open days). But keep in mind that this will be applied to all projects and resources : today, there is one only calendar. An evolution is planned to provided sevaral calendars and affect resources to one of these (Ticket #714).
Q2) My projects have many repeating tasks (e.g. weekly program meeting every Thursday for 3hrs at 3PM, Onsite backup tape change etc). What is the best way to schedule ongoing, repeating tasks like these?
Periodic meetings !!!
Q3) Is there a way to change the size of the top, horizontal menu items? (I can see how to change the left, main menu icon sizes).
No
Q4) Is there a way to edit the items on the main, left menu (delete, hide, reorder etc)?
Hide : remove rights on the screen "access to forms".
Reorder : change order in table menu (pay attention to preserve hierarchic position (idMenu = id of top menu)
Q5) What is the best way to add a field e.g. Add Skype ID to a Contact?
Add field in the database (table contact), add definition in the class script (/model/Contact.php). That's all