LLG, please try Alanon meetings. Alanon is meant for family and friends of alcoholics but I find it very helpful for family and friends of addicts (though in some groups mentioning heroin might not be acceptable).
From wanting to work in social services, always putting others before yourself, always seeing the good in people (is that the same as accepting things most people would not?) and dating addicts...I think you need to work on yourself. I am not saying that social work is wrong for you, only that that urge to help and fix others is something we see in Alanon.
I think all the men i ever was interested in were either alcoholics or addict (using or
dry or sober). My ex is using heroin, he has relapsed 4 years ago and is still going, meanwhile I am a single mom to our 4 year old. We were together 10 years! And he was clean 10 years (2 years prior and the first 8 years of our relationship). It doesn't matter now. He is an addict and has relapsed. His #1 priority is getting and using heroin.