I wish Madeleine all the best but I must admit my feelings towards this engagement are not good: they dated for very little time
They have been together for about 1½ years, the king and queen had known eachother for four years when they got married (one reason for waiting four years was that Silvia had promised to work at the Olympic Games in Innsbruck, otherwise they would probably have married sooner). It's not certain that a long relationship beforehand means that a marriage will last, sometimes people know from the beginning that a person is the right one for them.
Is it normal to have a video?
No, there is usually an interview, but the couple are already on their way home to New York, so I guess that the video is instead of an interview.
He'll probably getting a dukedom.
He won't get a dukedom of his own, but he may get his wife's ducal title.
Whether he is created a Prince of Sweden in his own right (like Daniel was) remains to be seen, but I wouldn't be surprised if he were.
It's unlikely that he will be made a prince, Jonas Bergström wasn't going to be made a prince so I can't see a reason why the king would make Chris a prince.
It's said in the official interview that Chris will not apply for the swedish citizenship. So he will stay british/amarican. And if I remember right titles are not possible / won't be recognized officially in any way in the american everyday life. So is it even possible to give him an official title / male version of Madeleines title (the title of a completely different country) if he doesn't want to change his citizenship?
As he has a British citizenship I can't see any reason why he couldn't get his wife's ducal title: Mr Christopher O'Neill, duke of Hälsingland and Gästrikland, to be titled the same way as it was intended for Jonas Bergström.
Chris will not attend the Nobel Prizes, at least this year, even when Daniel was engaged to Victoria he didnt go, he only attended when married.
Jonas Bergström attended the Nobel Prize ceremony in 2010,
http://tinyurl.com/bp8b45l , wheh he was engaged to Madeleine, there is no reason why Chris wouldn't attend this years Nobel Prize ceremony. Daniel didn't attend 2010, but that due to his kidney transplant, as he was on immunosuppressive drugs and it was considered unwise to attend such a large gathering of people.