Look here (where you post will get moved)
http://www.flyertalk.com/forum/infor...help-here.html
How long will you be living in Europe?
With Etihad Gold & Virgin Velocity Silver you have an overlap of ffp's. DL is a VA partner
Alaska has many partners, including Emirates, Delta & KLM
http://www.alaskaair.com/content/mil...-overview.aspx
From reading post in FT AS is a better ffp than KLM/AF
For your United flights you could join the United ffp and so cover the Star Alliance. Business class fares will build up UA status and then UA upgrades are possible.
From "Which ffp to join"
Airlines tend to treat members of their own frequent flyer program better than members of other frequent flyer programs. If you fly one of these airlines, it is recommended that you choose that airline. As a very general rule, it's best to maintain status on the airline you mostly fly.