I know I'm not an N, but I'm a J and a 1w2 and I'm posting this anyways in the hope that it helps. My answers might be similar to an ENTJ 1w2's, after all, considering the Te dominance.
What are the type 1 NFJ and NTJs setting out to accomplish in life? In their careers?
I want to matter. I want to be respected. I want love and appreciation and I want to do something that matters. It would be one of my worst nightmares, to die after a worthless and purposeless existence. My career goals are similar; wanting to do something
worthwhile.
What are their priorities?
Family, school/my future, and friends. In that order.
How do they deal with obstacles?
I either avoid them or tackle them head-on. There's pretty much no middle ground.
How do they prefer to navigate their interpersonal terrain?
I try to avoid small talk unless I actually care; my Fe is bad, so I feel awkward feigning interest in other people's problems. Otherwise, I'm very genuine and honest with pretty much everyone. I'm often better at one-on-one interaction, but one of my favorite things is storytelling to a responsive group of people who understand my sense of humor.
(If I didn't answer this question correctly, let me know... I'm not sure if I interpreted it the right way.)
How do you give fuel to and support type 1 NFJs? NTJs? How do you best support these people in any kind of relationship?
Respect, love, forgiveness. Easing off the internal pressure. It sucks when friends and family, thinking they're being comforting, add on even more pressure on top of the pressure I'm already putting on myself. The best response, in my opinion, would be telling me, in moments of insecurity and low self-esteem, reminding me that they don't like me because of my accomplishments, but that they like me for who I am.
As for giving fuel... I suppose putting things back in perspective. Reminding me of the big picture, and getting my head out of the little details. Grounding me and reminding me of how things really are.
How do others unintentionally drag them down and slow their efforts?
Since my efforts are very straightforward, this answer has to be straightforward too: If you aren't doing things correctly when I was banking on you doing them correctly, then you're slowing me down.

Beyond that... I guess if you mess with my mood, you're messing with my productivity too.
What are their blind spots? How do they frustrate others?
I dunno. You tell me!
EDIT: My answer to the question about "support"... It really only applies with people I'm close-ish to. And only when I really need support. So I guess it doesn't apply with "any kind of relationship".