1. The agreement which has not been renewed till this date is not legally valid.
Since the agreement has become infructuous, the conditions in the agreement stands revoked.
You can issue a legal notice to him to pay the arrears of rent and also instruct him to vacate after paying all the arrears of rent till this date.
After this you can file an eviction suit if he has not responded or is complying with the demands made.
2. The rental amount shall be based on the agreement already signed with him, anything beyond that shall be invalid. and illegal.
3. Dont be under the impression that court will entertain his claim, you have to fight out your case on the basis of merits in your side.
4. Your this question i absurd. Even before filing a case you should not think about the negative side or should not have a negative aproach.
You fight your case, if the lower court is not favoring you, then you may aproach the appellate courts.
Any judgment at this stage will not fetch you any benefit until you file a case and fight it out properly.