It is absolutely normal that you get weak sometimes. That is because you have a heart and because you have grown attached to him and a bit of „sunk cost fallacy“ (google it if it doesn‘t sound familiar).
Like giving up smoking, normal people do not lightly give up their significant other and it is hard to stay away, even if our reasonable brain parts say we should, because there have been good times that you would have wished to be the normality of your relationship.
Sadly, untill there would be radical and evdidence based and most importantly lasting changes, you are not in a relationship with a future.

Relapse into an unhealthy relationship causes more and longer lasting hurt for you, but it is very human to miss and have last straw hope, after having put in so much effort into a relationship with someone who - in the end - does not love you and the children like you deserve to be loved.