A: The security deposit is generally one month's rent. If the rent increases, the landlord can collect an additional sum to bring the deposit back up to the one month level. The landlord can use the security deposit to cover unpaid rent and/or the cost of repairing any damage to the unit that was caused by the tenant, over and above reasonable wear and tear.
A: Yes. The landlord is entitled to keep up to 1% of the deposit to cover annual administrative expenses, but the rest of the interest belongs to the tenant. The tenant can choose to have the interest paid yearly or at the end of the lease term, or applied to the rent.
A: The law says "within a reasonable time" following the expiration of the lease. To be on the safe side, it's a good idea to return the security deposit within 30-45 days after the tenant vacates the premises.