1. I am curious how this theology looks like in reality!
I guess the reality of this theology would look much like live at one of the homes of the L’Arche Daybreak community.
As to how it would look in ordinary life, if everyone would live by this theology I would not have a clue. As for me: I find it easier to focus on what is right and live that way. Also I found the bible actually is a channel for God to communicate through. I find myself living closer to God.

2. How would you define the relationship between theology and psychology?
Maybe Henri gives a theological answer to a psychological question. Namely: “You are a child of God” to “Who are we.” Also he fights the thought there could be a social or psychological answer to that question: it will never give a satisfying answer in the end. But in my opinion this psychological question is a result of a spiritual question. You cannot separate the question about your identity from the questions about your origin and destiny.
To other (real) psychological questions he does give a psychological answer: for instance he tells us to embrace our pain and claim it.

3. What is the allowed extent of a strong emphasis on the immanence of Christ.
(Some of my thoughts about that here.)
The allowed extent I guess would be there were it is still real; there where Christ really is present.

4. How do you value the emphasis Nouwen puts on the comfort dimension of the Gospel compared to the challenge dimension?
If by comfort you mean the thought that you are loved by God, then I’d wonder: is that really a comforting thought? To me it isn’t. The real comfort comes after becoming silent and listening to His voice.
The challenge I think is entering into a relationship with God. Being willing to surrender yourself, to become fruitful, to receive new life, to be molded.
So the challenge comes first: “Listening to the voice of God who says: you are my beloved.” the comfort follows by acting upon that voice.

(* Let’s try to keep in mind I was trained to be a technical engineer – not a priest!)