Yes
Yes the landlord can be sued for breaking the lease.
Yes, unless the landlord breached the lease in some significant way.
If the unit is rented immediately the landlord cannot charge you the rent for the rest of the terms on the lease, but may keep your deposit.
This depends upon whether that fee is quoted on your lease when you signed it. It is not there, then landlord cannot charge you because he rented the apartment quickly after you left. However he may be able to keep your security deposit if you broke your lease. If there was a lease, the terms are generally such that you are responsible for the rent for any month that the apartment is vacant from the time you vacate the apartment to the time the lease ends OR the apartment is rented out, whichever comes first. Since the landlord did not suffer any damage by breaking the lease - he rented out the unit just a few days that you left - there shouldn't really be any reason for him to charge a fee. But if that is stated on your lease then he has the right to do so.
It's not impossible, but it really depends on how the lease is written.
Yes, and will be upheld in court. Unless items are in violation of the Landlord act of that state. If the lease is not "breaking" your states landlord act they are valid even if they sound absurd.
It is unseemly that a landlord can charge a tenant for other than the items listed in the lease. You can pay them and take your landlord to landlord-tenant court for reimbursement, or you can approach a landlord-tenant advocacy to find the answer that you want.
yes
Nothing. The landlord need only give you the notice required by law (20 days in WA) and then simply move back in. The exception is if you have a lease--in that case, the landlord must honor the term of the lease unless the landlord and tenant mutually agree to break the lease. In that case, the tenant is free to demand compensation of the landlord for the landlord's breaking the lease.
Even if u are n a lease breaking the lease may jus mean the landlord can charge u a fee of some kind or jus simply not ever rent to u again. But if u DID NOT sign a lease it is ok to just leave. It is more proper to give your landlord a good 30 day notice just to b nice. =)
Only if it so specifies on the lease
Only if the tenant is still there.