AAQ, it’s interesting that you draw a parallel between yourself and Shimon Ho’amsuni. As you will know, he was able to expound every ‘es’ in the Torah, until he reached one he couldn’t explain; at which point he retracted all of his דרשות. The Gemoro (Kiddushin 57a et al.) ends the story by saying, “עד שבא ר’ עקיבא ולימד את ה’ אלוקיך תירא לרבות תלמידי חכמים”. In other words, Shimon Ho’amsuni’s initial position – that every ‘es’ has a דרשה attached – was indeed correct! It’s just that he couldn’t think of a דרשה for one of them; so it was left to Rebbi Akiva to uphold and validate his initial view by finding a דרשה for that את.
I think our case is indeed very similar. I agree with your initial position (based on the words of your teacher) that the concept of דעת תורה does not appear in Shas; and I fail to see how the Gemoro you quote contradicts this notion. The Gemoro simply says that Rebbi Yochanan wanted Ze’iri to marry his daughter, and tried to convince him to do so. How does this imply דעת תורה? I’m sure there are many baalebatim who would like to see their daughter marry a top בחור, and might try to persuade him if he was reluctant!