I feel very sorry for you here. But you are being very, very foolish to even think of consider allowing things to continue as they are.
Because as it stands on paper - you are the junkie, not him.
Change cards so he can't by drugs in your name- remove the credit/debit part of it, close open a cash card only. Anything.
Should you break up and there is a dispute about custody/maintenanc all the drugs are in your name. If you want to leave him at any point, he can happily prove YOU are the junkie not him due to the long, long list of medication you are "taking". Consider that.
Some other things to think about.
First off - if he kills himself because you try to get help for him , what is the difference from the slow suicide he is currently committing also faciliated by you? I would say, there's no difference at all - in fact thins way of death is more on you because you are actively helping him obtain the drugs.
The points made by previous posters regarding your children are valid. You are allowing a seriously addicted individual to care for your children and you are aware of the addiction. You are in fact, aiding him to hide and continue this addiction.
If he is so far gone that he has the shakes, then it is INSANE to even think that it would be medically safe for him to attempt to detox on his own. His liver doesn't need more drugs (lyrica) it needs less, and someone would has been addicted for that long cannot , swap out the codeine with Lyrica for 5-7 days and everything will be hunky dory. He needs full time residential care and a medically supervised detox. He will be sick.
Why would you allow your children to witness this?
Your children are going to go back to school and when friends ask them what they did on holidays it'll be " Mum drove us to multiple chemists so Dad could go in everyday" . Or are they too young to notice, and that's okay then.
That you know he's off his head all the time, yet has a role where being on drugs is a problem, makes me think he's in a position of responsibility to the public in some way. Does that not make you feel sick, knowing you are condoning and supporting a man working in this situation when you know he's not capable and could do serious harm to someone?
I do feel for you, but you are burying your head in the sand badly.
As a first step, cancel your card and get another that has no credit facilities. Get your name off all this shit. Tell him to open his own Paypal
Do something though, because he will die if you don't. If you actually love him, get him some help.