Can't help you with 1 or 2. As for #3, people have crossed with lesser boats properly prepared. I think the problem would be that it would cost you quite a bit to get the boat (especially of this age) ready for the trip - including paying for a lot of things that you would probably not need if you are going to use it for a coastal cruiser in Europe - e.g. a proper lifefraft and EPIRB.1.Critical points for a 1974 Cape Dory 25 survey before to buy ?
2.Options for boat delivery in EU?What documents must be provided?
3.It is able, by technical view, to cross the ocean during a optimal weather window?
I agree with the suggestion about the CD 25D which is a much nicer boat than the CD 25.