@love15
You've been with him 9.5 years ffs. Haven't you wasted enough time on the selfish prick ??
You said it yourself, Partner has always looked elsewhere - messaging girls online/Facebook/general social media....
It doesn't matter whether you 'think' drink/drugs are to blame (he still chooses to drink/do drugs AND look elsewhere for women
). The fact is, He's an unfit Father and an unfit partner, and he won't* 'change' ffs !
To answer your question, No, you cannot 'fix' him 
You need to shift your priorities pronto.
Your DD NEEDS you to protect her !
Selfishly staying with an alcoholic drug addict is abusing your own DD ffs !
Stop behaving so badly, and step up as a parent, because she needs you ! (while he is a selfish bastard, who only cares about himself, but he is an adult, and as such, can behave how he pleases)