I think his weakness is justified given his trauma. Past experiences and conditioning in which every time you make a move, you end up fucking up can lead to a person being quite hesitant and being very deliberate in their actions. He's treading on thin ice and he knows it. My biggest compliant is how he doesn't contact the authorities or police, especially earlier (though the author does give several reasons for why he doesn't later). Even if he wants to kill her by his own hand, the death penalty will be the most likely outcome given the circumstances, though with the SD card plot line, this option is no longer available, really.
Honestly, I think he should commit suicide because it would be the best way to get revenge and mitigate the damage incurred onto others. Think about it: if he kills himself, then the Yandere bitch will have no reason to keep pursuing him or to live herself. She will be forced to experience the same loneliness and isolation he went through and most likely kill herself as well. He has few friends and people close to him because of her, she absolutely ruined his life and continues to rape, abuse, and torture those close to him, and she only brings forth pain and misery where ever she goes. Suicide, then, would ease literally ensure that she either has another case of amnesia or is forced to commit the same act, thereby ensuring justice. It's the tragic irony that this is probably one of the better plans given that even if she doesn't kill herself over him, it is likely his allies will kill her for him.
@Reqqles
Kinda addressed you points without realizing it, but yeah he can't call the cops because the videos she has will automatically upload and ruin the lives of everyone around him.
@OraOraApril19