@Mandy406 I'm so sorry this happened to you. It sounds really dubious.
I'm surprised that anyone would agree to a $350 cleaning fee for a 4 day stay in a one bedroom apartment. It appears that the host is perhaps trying to dodge taxes or something by charging such a large cleaning fee. What was the nightly rate for the place?
You can actually report the listing if this seems like serial behavior from the host. You should read some past reviews and try to determine if this is a pattern of behavior. There's a report button at the bottom of every listing.
The claim sounds ridiculous. Crumbs are not something to file a claim for. Cleaning up after guests is a cost of doing business, and that's what cleaning fees are for. Even a kettle (hard to ruin??) is not worth a claim. I don't know what this host is up to, but don't pay the claim and stand your ground.
But I'd also say that even after this bad experience, please give hosts the benefit of the doubt. I believe this situation is the exception, not the norm. You said you'd had many good AirBnB stays in the past, so hopefully this is a one-off and you can continue to have good stays in the future. Kia