If you believe you can convince a court that your rent was not late, then you can attempt to prove that case in small claims court. Also, depending on the facts, you may be able to argue that the late fee was waived by course of dealing or that it was excessive (I can't comment on that as I have no details).

When a security deposit is returned late you can sue for the return of the entire deposit (and potentially double that amount if the court finds bad faith), but the governing statute, ORS 90.300, appears to allow your landlord to assert a counter-claim for the money he claims he is owed. Still, that puts the landlord on the defensive.