Charlton had brought himself to admire this dispassionate temper.

A man of Charlton's temper who is really in love, can bring himself to admire any traits in the object of his love.

Had Helen Minorkey shown some little enthusiasm, Charlton would have exaggerated it, admired it, and rejoiced in it as a priceless quality.
As she showed none, he admired the lack of it in her, rejoiced in her entire superiority to her sex in this regard, and loved her more and more passionately every day.

And Miss Minorkey was not wanting in a certain tenderness toward her adorer.

She loved him in her way, it made her happy to be loved in that ideal fashion.
Charlton found himself in a strait betwixt two.