EU/NON-EU COUPLE NEEDS ADVICE,SPECIAL SITUATION!

Hi everyone, great forum! I'm looking for advice regarding my situation:
I'm a Danish girl with an American/Brazilian boyfriend. I'm currently travelling back and forth between Denmark and New York (where he lives) on a tourist visa, and now we're sure we want a life together, preferably in the EU. I started checking immigration possibilities in other EU-countries, as Denmark is a special case for us who live there, which some of you might know of. What I would like to get some advice on, is whether it's possible for me to use the EU-treaty-rights to sponsor my boyfriend to come live with me in the UK? I would go there to work for a year and then start studies. How does it work when the non-EU spouse applies from outside of the US? We plan, under all circumstances, to get married in the US this spring. The thing is, we will not have been living together for longer than a few months at the time, always on his adress here in New York, me officially resident in Denmark. Will it be hard to prove to the British authorities that this is not a marriage of convenience?
Thanks in advance!

Will it be hard to prove to the British authorities that this is not a marriage of convenience?

You can submit phone bills, emails, pictures etc if you like.

If your soon to be spouse is planning to apply from outside the US, he would need to prove that he is lawfully resident in that country where the application is made. Where are you guys planning to apply?