I can't speak for Ramya, but as she said Sir Thomas had kind intentions, but execution was horrible. The idea of "preparing" Fanny for mediocrity is offensive(to me at least).

from ch2
“as to the distinction proper to be made between the girls as they grow up: how to preserve in the minds of my daughters the consciousness of what they are, without making them think too lowly of their cousin; and how, without depressing her spirits too far, to make her remember that she is not a Miss Bertram.

Their rank, fortune, rights, and expectations will always be different. It is a point of great delicacy, and you must assist us in our endeavours to choose exactly the right line of conduct.”

Why is any special "line of conduct" required? The simple knowledge for Fanny that she had no dowry accomplishes it all without any pointed "preparation" required. I think he is wrong.

So even though the mediocrity remark related to the topic at hand, he also said The principle was good in itself, but it may have been, and I believe has been, carried too far in your case....little privations and restrictions that may have been imposed..

No, no the principle was not good. He doesn't want Fanny to harbour resentment against Mrs. Nasty, but I will for her! I think the fact that there was a fire when she came back to her room shows that despite his raging at her, he does know that she deserves better treatment.

When Mrs. Norris is complaining of Fanny later...she likes to go her own way to work; she does not like to be dictated to; she takes her own independent walk whenever she can; she certainly has a little spirit of secrecy, and independence, and nonsense, about her, which I would advise her to get the better of.”

As a general reflection on Fanny, Sir Thomas thought nothing could be more unjust, though he had been so lately expressing the same sentiments himself

I wonder does that mean Sir Thomas just at that point realized he was unjust, or is it the narrator telling us the irony of it?

I agree with you that Sir Thomas thought Mrs. Norris wanted Fanny from the beginning, and just was glad that he might be relieved from the general expense when Mr. Norris died. I think he intended to help monetarily all along.