***** NOT A TEACHER *****
(1) I know that you want an honest opinion, so I most respectfully and gently suggest that your two sentences do not sound too
natural -- in my opinion, that is. In other words, if a native speaker were to read those two lines, s/he would immediately realize that
a non-native speaker had written them.
(2) I am no writer (!), but I suggest something like:
A few days ago, Kathy discovered that her husband had been having a gay affair. Failing to persuade her husband to end the
relationship, she pushed him down the stairs on the fifth floor.