Jet2 don't codeshare with KLM so I would see AMS 3x daily as very optimistic, frankly senseless.
DSA isn't a Jet2 base yet so New York would also be very very optimistic. In fact any new bases including BLK (as it's mentioned far too often) ever seeing a 757 are doubtful as they aren't planning to add any more to my knowledge.
Bucket and spade, and city break flights using a 733 are potentially more realistic, and I'm sure DSA is continually being evaluated by LS as a potential new base, along with numerous other UK airports. LBA, NCL and MAN don't have DUB or EWR yet so let's not get carried away.