I see no reason why the Northeast would trend toward Trump at all
Well, some states must trend Republican in every election, and it certainly isn't going to be the South or the West. What areas do you see Trump doing relatively better in, compared to the national swing?
I don't think any region needs to see a significant Republican trend with Trump on the ballot. A good prediction shouldn't assume an even split between states trending GOP and states trending D. It should evaluate each region individually, and Trump is a terrible fit for the northeast.
No. In every election, roughly half of the states trend D and half trend R. Remember we're talking about
trend not swing. In 2012, 23 states trended D and 27 states trended R. In 2008, 28 states trended D and 22 trended Republican. In 2004, it was also 28 D and 22 R. Unless Trump were to overwhelmingly win a large state like California, we can reasonably assume at least 20 states will trend Republican, and at least 20 Democratic.