First off, trying to view the 2013 New Jersey election through the lens of a national election is a mistake. Historically, New Jersey Republicans have been pretty well insulated from national trends (except maybe 1995) and do well when Democrats are running the show in Washington. And let's be honest, Christie is probably one of the most anti-Washington Republicans in the country right now.
Anyway, back to the districts. District 2, as you said, is more Democratic than baseline. Still, I'm accurate in saying there are a lot of Republicans there who will turn out in droves: This is a Republican County on a local level. It's questionable how strong Democrats are going to be in Atlantic City. This is a district that got hit hard by Sandy.
Republicans picked up District 4 in 2009, the last time Christie was on the ballot. It's very independent heavy. So too is District 14, and while Greenstein is popular, so too was Inverso. Yeah, I admit, it's been a while since Inverso was on the ballot last, and Roma Bank probably doesn't make him more popular. Still, these are just the kind of districts that are going to go nuts over Christie this year. I wouldn't want to be running downballot there as a Democrat this year (or, coincidentally, as a Republican next year).
I don't think the GOP will actually win the 18th, because I don't think a Republican can win anything but a sneak attack there. If Stahl wins, it'll be a surprise to everyone.
If I'm doling out money for the Senate GOP, the bulk goes to win 2. Inverso gets whatever he negotiated when Kean Jr. got him to run in 14. I'd pay for a bunch of polling in District 1, and I'd try to get Christie to visit as much as possible. Ultimately only the Assembly seats there look vulnerable. I'd make an arrangement to have a full-time intern out on District 18, because I think this is the exact kind of area the GOP needs to improve its performance to be more credible statewide in 10 years to combat the inevitable decline elsewhere. Wouldn't hurt getting more people operatives with the territory.
Democrats running the show in Washington? Last I knew Republicans controlled the house.
I'm also looking at what happened in 2009, when dem turnout was completely in the toilet. Democrats lost just one seat and even that loss was a fluke.
And these indpendent voters have been voting for Democrats(except for Christie) for years. They voted by about 20 points for Obama and even solidly for John Kerry in 2004, who had about as a much appeal and charisma as a rotting 2 by 4.