@Symbolika1
From his pov before and after he unknowledge that all was granny's doing=> It's a full trauma.
Usualy in drama's lady's are mostly putted in this kind of physical/psych.abuse - here it is a grown up man. But what is shown is not him killing granny. It's not a direct revenge. It's his overcoming it. With Xiao Yao's help too. Don't you like it better? I found it more subtile... :)
It's another bad trauma for him even though it's not physically hurting him. He's both emotional and physically hurting. (Especially because he's shown to pride in being gentleman). But i understand this whole plot though ...definetly not to show "how weak TSJ is", but to show readers and XY herself know that how much TSJ weigh in her heart more than she thought and she's been in long love sickness for 10 years, both of them. San Tier Er telling to her face that it needed both to act out in relationship. (TH is favoring XY to act in the scene, helping her man from H&YY) .XL involvement too yep. I think its fine plot.
Edit: This also lead CX 's judgment of Jing in how weak Jing is and consider not suitable to protect XY (guessing its similar what most XL fans think too ) and that will lead him to do what he did to jing later then