Has Cruz told Graham to stick his endorsement somewhere yet? If he doesn’t that is pretty telling.
Nope. What it tells is that Cruz wants to win, as he should. Any endorsement that is not destructive should be accepted. Graham and Rubio both dislike Cruz, which is a big plus. If they endorse him anyways and bring any voters at all (I'm not sure their endorsement matters), then Cruz should take the votes.
If Bernie Sanders endorses Trump, I hope Trump will welcome Bernie's voters. While they have different approaches to solving problems, they agree on what the problems are a lot more than Trump and Hillary do. A Bernie endorsement would not imply that Trump is a socialist, just as a Rubio/Graham endorsement would not imply that Cruz is pro-Amnesty.
Where is the list of endorsements that Trump has rejected?
He won’t. At this point it seems he wants the presidency at any cost. What will be priceless is when Jeb endorses Cruz and seeing his supporters reactions to that. Cruz is playing on both sides of the fence. He’s appealing to conservatives for their votes, and at the same time selling out to the establishment for their loads of money. Very soon people on both sides of that fence will kick him to the curb.