Was my defense of someone who was insulted, with the intention of repelling backbiting, right or wrong, especially given the fear of falling into backbiting and ill-suspicion when feeling jealous, and with the feeling of waswasa (whispers/obsessive thoughts) and hesitation in dealing with situations that might involve injustice or backbiting towards others?

If the suitor has defamed someone, he has committed a wrong, and your defense of your Muslim brother is a great act of devotion; for "Whoever defends the honor of his brother, Allah will turn the Fire away from his face on the Day of Resurrection." You must adhere to the Shariah ruling on backbiting and seek refuge in Allah from the whispers of Satan. You should seek excuses for people and assume the best; for "Avoid much assumption. Indeed, some assumption is sin." Remember that you are strangers to each other, and communication is not permissible except out of necessity and to the extent of that necessity.