1.DO not worry as you can not be asked to vacate the property before the expiry of the 5 years of tenancy.
2. Since you have not got possession of the agreed area for which the rent was fixed you are not bound to tender full rent as well and hence you can accordingly deduct proportionate amount for the full rent.
3.Howeevr before that do send him a written notice seeking delivery of fullarea for tenancy and adjustment of rent till this si done.
This will help you later of the dispute reaches to court.