In respect of the most recent one, moving the embassy to Jerusalem, it could simply be a symbolic move to appeal to his supporters. There's an interesting analysis in the Financial Times, written by a former US Ambassador to Israel which says that having Pence with him when he made the announcement is clearly aimed at the Evangelical Christian support that Pence commands and which is determinedly pro-Israel. Yet on the other hand, he then signed the waiver which allows the POTUS to delay the move, which had been voted through some time ago and well before Trump. Partly that reflects the need to actually build an embassy but if he was deadly serious about this he could have simply moved the Ambassador and his key staff to the existing US Consulate in West Jerusalem and designated that as the US Embassy.
I suspect this all ties in to a move towards a peace plan. That may seem a bizarre thing to say but there's a Saudi proposal doing the rounds that has a number of proposals which the PA are certain to reject, including locating the capital of a future Palestinian state in Abu Dis, which is on the eastern edge of the Jerusalem municipal area. My suspicion is that, by putting completely ridiculous and seemingly confrontational proposals on the table, Trump is using these to make more conciliatory proposals appear more acceptable. Given his self-promotion of himself as a master negotiator, this is a pretty standard if unsubtle negotiating tactic that he's used before.