Have had a lot of experience with NPD and BPD. I agree with your judgment exactly: that Trump displays about half of those traits, but the ones he misses on, make NPB pretty unlikely from my standpoint.
Nobody here has talked about how self-assured and well-adjusted his daughters are, and why his very likeable sons think he is an Olympic deity. Every mom and dad knows that you cannot fake good kids - that your adult children are huge commentaries on you as a person.
Every single person I've counseled who manifested NPD and BPD had very dysfunctional families. Without any exception. ALMOST without exception, a person with NPD or BPD has most of his family members who can't stand to be in the same room with him.
I have to say, in good nature ... if a person is desperate to minimize Don Jr. and Ivanka, that they are too emotional about the situation to judge Trump even-handedly.
For me it's a poker tell, whether a person responds to Eric, Don Jr. and Ivanka by waving them off, rather than simply acknowledging them as a big plus for him. Donald Trump's kids are better-adjusted than mine are; how 'bout you other mommies and daddies?
I don't say it proves he's a great guy. If he called and invited me to dinner, I would flatly decline to go. Would like to see points made on both sides of Trump's ledger, though.