I'll try to phrase it again. Is it possible, in principle, to give practical guidance regarding parents on the basis of the laws of honoring parents? I'm intentionally trying not to get into a specific situation and to stay at the level of principle. In a situation where a parent emotionally harms a child—which is inevitable in the parent-child relationship—is it possible to issue a halakhic ruling that says how much the child has to "put up with" from the parent in order to honor him? The sources are varied, and it's hard to draw a definite inference from them; are they useful at all? Since every parent-child situation is complex, is it even possible to address them halakhically, given that it's hard to assume a halakhic decisor can know all the details necessary for full judgment (and it's doubtful even the people involved can know them).

(The referral to a psychologist [a religious one] was so I could get halakhic advice from him, which in my view was out of place.)

In questions like the one you raised, there is definitely room for assessment, and usually there are no sharp lines. But it's worth hearing from a psychologist who can say what, in his opinion, the consequences are, so that you can make a decision. I don't think it's always possible to derive an answer directly from the sources, but usually they can be used to help reach a decision. From this you'll understand that turning to a psychologist on such questions is no less important than turning to a rabbi, precisely because this involves assessing reality and not deriving an answer from discussion of halakhic sources alone.
As for the referral to a psychologist, again I'll say that I see only a general statement here, and I don't know how to relate to it. There are certainly situations where I can see referring someone to a psychologist so that he can make the decision. Just as one turns to a doctor regarding fasting on Yom Kippur or desecrating the Sabbath. In principle this is a similar situation. That's true even regarding the psychologist's making the decision. But if we're talking about advice (as you wrote here), then certainly that has a place and there's nothing wrong with it.

To the questioner,
I have to say I was really shocked by the sentence:
"A parent emotionally harms a child, which is inevitable in the parent-child relationship."
Why would a parent emotionally harm his child? That is absolutely not inevitable; it's a well-known source of all sorts of emotional disorders and distress.

Shai,
Every parenting style causes some degree of harm. Of course, the most severe and basic injuries are not intentional. It's not such a disaster; we're not porcelain dolls, and it's possible to live with it. But my question is how much I (or anyone else who gets stuck with this problem) can do what is healthy for him at the expense of honoring parents.

On this, see here:

כיבוד הורים וטריטוריה הלכתית

A., R.,
That's why it's recommended to consult a psychologist; usually he has experience and knows what is liable to cause serious harm and what isn't.