Hello some update:
issue 3: resolved assigning to css class of  additional attribute's basic information tab the value :   input wXXp  where XX is a number.  If you have a better solution or suggestions they are welcome.
about the issue 1 in the previous message I resolved clearing cache and launching a rebuild both in attribute  and in category. Now when i edit a variant all the value in the list are displayed correctly in the list. 
to explain better the issue number 2  i link a short video screencast 
https://www.screencast.com/t/f8zyhpX6N
this i still have to figure out how to resolve
thank you for your time