I'll bite too. Willy: impact of parents. Dr Obeidi shows how he has been influenced by his parents and qualities he has gained from them. Willy also has been influenced by hs father too. In addition, pride in hs work. The only thing I can think of with Spencer is great instincts although that is stretching it a bit!
The other one I am reminded of a bit on further reflection is Martin Finch. This is because he is someone who has made it good, made a success of himself, shows his potential, and then is entrusted with a job, which then doesn't go quite according to plan and events backfire on him. There is also the theme of having to account for himself at regular intervals and coming in for some heat and criticism. Of course, he is distracted from his objective in a way that Dr Obeidi isn't.
And then there's Gilbert, with his sense of duty.
I've been trying to synthesize some of these and two half-remembered quotes are knocking around in my head. One is a discussion about the extent to which Johnny plays damaged people, and the other is a fan's comment that Johnny repeated: thanks for playing all those poor people. I think Dr Obeidi is another of those poor people; he finds himself in a nightmarish stituation but who does the best he can. Another recurring theme is the theme of the true story that nebraska picked up on.
"Luck... inspiration... both only really happen to you when you empty your heart of ambition, purpose, and plan; when you give yourself, completely, to the golden, fate-filled moment."