My Mother-in-law is going to fuck our credit & Husband is going to let her 🙄

I need some guidance or something here…

My MIL has asked to borrow husbands credit card to buy my SIL $700 helium tanks for her party supply/decor store that they own. (Multiple tanks over the course of the next few months. Not just one $700 purchase btw) They have guilt tripped him by saying if they can’t but a new helium tank, they will have to close her store. So he told them he’d talk to me about it and I don’t want to be “controlling” so I told him if he truly believes they won’t mess up his credit and will make the payments, to do what he needs to do. BUT…. They have opens credit cards in his name before and didn’t make the payments and have been a very big contributor to his poor credit. Which he has finally almost full repaired for us to be able to buy our own home. Which is really important for us to get to do. So I told him that if they mess it up or miss one payment it needs to be cut off immediately. He agreed but I also know that he will hide it if he can and if they miss one, he’ll make the payment instead, making us short on money. I do not have access to any of his funds so I can’t look either.

His family is the most childish/irresponsible bunch of adults I’ve ever known and I honestly wouldn’t put it past them to purposely mess his credit up and sabotage us moving, just because. They don’t even visit with us but they’re vindictive like that. But I know if something happens and his sister has to close her store, it would come back on me for not letting my husband give them his credit card and he’d hold a chip on his shoulder for it too.

He literally said to me when I was questioning whether or not they’d be responsible enough to make payments and not mess up his newly repaired credit, “well, I’d rather my sister not have to lose her store”……….

I was like ARE YOU KIDDING ME. I think you, our son, and I deserve a nice home to call our OWN… more so than your sister needs a store that she never even works at.. which is why they can’t afford to buy any helium in the first place. She wants to be able to say “she owns a store” but never wants to actually open it and WORK.. can’t make money if you never open your store for customers to come in 🙄

Anyways.. sorry for the rant. What should I do?!?!