1) Yes, Trump stole the idea from Rand, but it's a rockin' great idea that's been taken to the 2.0 level. I suggested a few days ago that Rand could have chosen to announce he was boycotting the debate whether or not he qualified for it, then do well at the IA caucuses anyway, as a power play to show the MSM he was not dependent on them. Trump has taken the idea to the next logical level. Result: he wins the final weekend's PR battle before IA.
2) If Trump goes through with the boycott, yes, FOX was asking for this rebuff and humiliation---and beyond FOX, the rest of the media as well. The network's memo went back into bossy mode, dictating that Trump would have to accept the same stupid attack poodle questioning and irrelevant PC questioners he objected to months ago. That showed the media has learned nothing, and wanted viewers to even forget there was ever a controversy over the appropriateness of Megyn Kelly's questions. Trump's response has put the network firmly in its place and punished them, consistent with the anti-establishment confrontation dynamic of this primary race.
3) Trump has stolen a number of other tactics of Rand's, including the "news bomb" method of finding legitimate ways for staying in the news, and deflating bad TV interviewers. If Rand had even part way continued to do what Trump has been doing start to finish, he would have been in a much stronger position.