I also wanted to have a go at it but had many of the same problems as yourself.
A. The nurse seems to be talking either to the patient, which can't really be or to the 2 men who are perhaps already in the room, and turns to look out the window as he speaks. I think the clash referred to is he's looking out the window yet addressing/lashing someone in the room. But what can he mean..the second damn time? and how can a tone be both lashing and cheerful?

b. I think bedroom is simply referring to the patient's room in the clinic, with no other significance.

c. Mystified.

e. Yes, I think Valery is the nurse. I suppose you can presume there were police and there is no funny business going on in the clinic or there were not and so everything is not exactly legal. As to looking out the window, I don't think it is significant.

d. Yes, I think she crossed a physical border to participate in some dodgy drug trial.

I'm having trouble also with .....For once only, maybe the right one. The right what? It doesn't properly follow I had to fix it for us Lucien

and

A wet and repeated slap against the floor. What is this?

and
The human crane behind the doctor leaned forward in her direction. Is this the attendant who was behind the doctor or has the nurse re-entered the room?

Sorry I'm not much help but I've read it many times and can't make any more out of it than that.

Edit: And I don't think the writer is a native English speaker.