I don’t think you really can do anything beyond doing what you are already doing, offering support/to be there if they seek help.
The best thing you can do is work on yourself, protect yourself and your finances etc., while waiting to see if they seek help.
Missing work, racking up debt and asking to ‘borrow’ money are all bad signs in my opinion. The blaming you – bringing up times you’d fallen short as a partner- in order to create a reason/excuse to use and to try to get money by creating guilt is another manipulative tactic you will see partners of addicts (and parents of addicts) mentioning on here. My addict partner has even admitted to causing/creating arguments/strife between us so he can use it as an excuse to get drugs so he can make himself feel better… he will also threaten to get drugs if I don’t behave how he wants – which doesn’t work now as I’m at the stage where I don’t care if he uses. I want him to stop but I’m not the cause so if he uses or not is his decision/responsibility and nothing to do with me.
Mine also does the turning the house upside down thing… for a long time I did not have permission to clean the house or touch anything because I might disturb, hoover up or accidentally throw away some crumbs he’d dropped or forgotten about.
I’m stuck because we have a child together and I’m currently waiting to get rehoused. If I didn’t have a child with him then I would have been long gone and just supporting him from the sidelines.
Life is short and addiction seems to be super complex – so no matter if the addict wants to quit, it doesn’t always work that simply. That’s why you see people doing rehab more than once.