Love letters
Woodward ironically states that Trump and Kim Jong Un send "love letters" to each other. This is ironic because they don't actually send love letters and in fact run countries that are at odds. Nonetheless, Woodward is trying to insinuate that their relationship is very close, and therefore chooses to comedically call them "love letters."
Someone different
Woodward argues that the American vote for Donald Trump in 2016 is significant. Many people voted for Trump as he seems to be different from the typical politician; however, Woodward shows that ironically, different doesn't necessarily mean better.
Pulling the strings
Ironically, although he is the president, Woodward argues that Trump is not the one pulling the strings. This is ironic because we might expect the President to be in charge.
Tough on Russia
Trump often maintains that he is "tough on Russia," and this is often a key statement in his campaigns. However, Woodward argues that he actually doesn't say anything negative about Russia or Putin, and cannot be seen as tough.
Trump
Woodward points to the fact that Trump is depicted as an ironic and comedic figure in the media. Irony is a key comedic device, and it seems that Trump is an easy target for comedians.