Itch can close a project if it breaks a rule or law, some creators sell assets without having the copyright, sometimes they are stolen assets, etc.
Normally when that happens, Itch tries to return the purchases, but this will surely depend on the time that has passed, if it was a bundle or not, etc.
But as you can understand, if that content is stolen, Itch cannot leave it in its store.
Itch does not charge a service fee, each developer can choose to share a percentage of the sale, but it is not mandatory, some developers set the value to 0% and Itch receives nothing.
Other developers do direct sales, so Itch is not even responsible for the sale, even if the game or asset is distributed through Itch.
Sometimes the administrator reads and answers the messages, try to put the confirmation number that you received from Itch when you contacted support, so, if the administrator sees your message, he could give you a more detailed answer.