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