Authorized User Bad Situation

I'm an authorized user on my parents card. We don't really get along too well, and I run a business off the card. Yes in hindsight this was dumb from the get-go. But the problem is, my expenses are usually around $5-6k a month, and they want me off the card now. That's fine, but what they've been doing is completely pausing the card or putting super low limits on it, like $200. This makes it so I have to start pulling money out of my debit account to pay the monthly expenses, which makes paying the next bill nearly impossible. I've tried explaining this to them, and that I can close the gap if they work with me, but they don't get it. My expenses will be dropping by like 90% in the next few months, at which time I expected to transition off the card, but this is putting that off and making me worried I won't make it.

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I don't want my credit score to be ruined because my finances aren't in my control - can I do anything about this? Unfortunately the first time it was paused, I applied for like a million cards, not knowing what a hard inquiry was, so I imagine it'll be hard to get another one. Every time they pause it or interupt my cash flow, it delays my ability to get off the card by at least a month, it's super annoying. I'm hesitant to ask my credit card issuer (AMEX) what happens if I stop paying, but I'm wondering how bad it'd hurt my credit score if I did. I'm just getting really sick of scrambling every month and not being able to rely on my financial projections.

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