Two part answer
a. The BrahMos-A, which is what you are referring to is a stop gap till the BrahMos-M comes online. It is expected in approx 4-5 years from now. This being the main reason for the low numbers of the BrahMos-A.
b. The 2 you are talking about are what were handed over for testing in 2015 to the IAF. Post that a squadron (Tigersharks) has been designated for the operational role. Induction of the modified Sukhois has started for this squadron.
My guess would be 1 more squadron may get operationalised once you have completed induction of this squadron. This would take you to 2025. Post which the BrahMos-M will come online.
The 40 MKIs capable of firing Brahmos-A will be distributed to all squadrons in groups of 2-4 depending on the need. The Tigershark squadron will have 8 due to the need for sea strike.