Op, I just want to tell you that it’s ok not to accept that a partner has an addiction, if that addiction impacts your life negatively.
I wouldn’t be in a relationship with anyone who was an alcoholic, a gambler, a very heavy smoker, very obese through food addiction........
You should value yourself enough to choose a partner who can look outside of their addiction and enjoy the world and all it has to offer, rather than the narrow focus of where to get their next fix. You are missing out on so much.
Also, I’ve been on universal credit and it’s about £320 per month, not including housing, so there’s no way your partner isn’t doing something to obtain more money.
If he’s getting anything on credit, consider you may be involved in the repayment of that debt and it won’t be fun. How will your partner support you with that scenario?