Since your not married his bills should be his and your bills yours. Living expenses i would only pay if they are for everyone and only for a designated and short time. I wouldnt be out buying him new clothes or anything like that. If you're paying his past credit cards that were used to buy drugs then you're paying for his drugs and taking away his consequence.
Before you get married you may want to set a boundary that he has to have his finances in order. if they arent then you're going to be dealing with this forever. i had to learn that lesson the hard way - I've supported many ex's and so far they're all still broke and unemployed. good riddence in my case.