The Danish are not interested in selling it, nor does it seem that Greenlanders are interested in declaring independence and then voting to join the US. (IIRC such a move was polling somewhere in the single digits.) A military takeover would go over poorly. Even if it went swimmingly, it would backfire, as an on-the-fence Europe would break from the US orbit, end or reorganize NATO, and establish much closer trade relations with China -- the latter move is already being pushed in certain quarters, on the grounds that it's growing increasingly necessary for the EU's economy.

Highly doubt. Denmark has been quietly moving in troops and supplies

Somehow I doubt it. Trump talks a lot of stuff that he hasn't been able to do, like lowering prices on food and gas.