There are 2 issues here.
The applicable date of the increase and the amount of the increase.
With regard to the applicable date, the applicable date starts from when the old rent finishes which is generally the review date.
If the rent takes 12 months to review, then the increased rent will be due not only from that day forward but also in respect of the previous 12 months. It does apply in retrospect.
The asbestos is not normally an issue provided it is not disturbed. If it’s something which you are responsible for removing under the terms of the lease, it may affect the rent. What should not affect the rent already improvements you have made. They are disregarded.
I don’t know where the surveyor came from and whether he was mutually agreed between you but it would be worthwhile getting another surveyor to give an open market rent in view of what you have said about the adjacent units.
Meanwhile, you need to keep paying the rent and I would suggest that you paid it at the increased rent while you argue so that the landlord cannot allege that you are in arrears and try to foreclose on the lease. He does not need a court order to do that if it’s a properly drafted lease, he can simply lock you out when the rent is 14 days in arrears.
Here is a most informative article on rent reviews in commercial property which will really help you.