yes, your landlord can charge you this fee.

You will have to evict here. Best to consult with a landlord/tenant attorney to assist you.

You are a guest. You can be asked to leave.

Check the language in your lease agreement with the tenant, but if the damage was not caused by your tenant's actions, they may not be responsible...

you will have to begin the eviction process to have her removed from your home.

Best to consult with a real property lawyer. You may be able to quitclaim the property from brother to you.

you could file an action against them for the damages they are causing to your credit and for the collection agencies actions.

I agree with Mr. O'Brien. Start the eviction process immediately.

Yes, you should attend the court hearing.

There is no limit. If your lease is up, and you are renegotiating a lease, the landlord can increase the rent to as much as he/she would like.