He needs to see a medical doctor to withdrawal from alcohol n benz its extremely dangerous to detox with this. We cannot give medical advice here sorry (see rules) but we can give support n advice based on experience.
First of all - welcome to the forum n secondly, so very sorry that you are going through.
Basically your bf has an addiction. Sometimes 1 min addicts can now of the dangers or be going through something unpleasants n vow never use use again, the next they want them as if its never happen n really they turn into someone they're not.
You say it's devastating you. What are you going to do FOR you to make sure you are ok. There are meetings for friends / family or haddicts called sl anon. Would you consider seeing if one is in your area n go? It may help you. Also please keep posting n reading there are people who will be here for you who know what you are going through.
Hugs n take care, thinking of you
Evey xoxox