Short answer is that there's no straightforward way to estimate max charge/discharge current.
The limiting factor is internal temperature, which should be kept well below the boiling point of the electrolyte. Many supercaps use ACN in their dielectric which boils at 82C, and they typically rate the max operating temperature at 65C.
For "standby" applications where the supercaps are rarely charged/discharged, such that the case temperature always relaxes back to the ambient temperature before the next cycle, you can make a very rough approximation as follows: Your 1.5F cap has a mass of 9.1g. Maybe 3g of that is dielectric. The specific heat capacity of ACN is ~2.2 J/g/k. Raising its temperature by one degree C requires 6.6J of energy. If your ambient temperature is 25C, and you limit the internal temperature to 65C, your max temperature rise is 40C, which takes 264J or energy. This is a lot more than the capacitor is even capable of storing (45J). If you actually want to charge it that fast, that begs the question "what the heck are you using the supercap for". Otherwise, charge/discharge current for standby applications is effectively unlimited (at ambient temp of 25C, anyways).
For "cycle" applications where charging/discharging happens frequently enough that their case temperature remains elevated above ambient, you have to estimate the case temperature (which replaces ambient temperature in the math above). Vendors are not going to provide this. It's too dependent on factors outside their control (orientation, proximity to other components, available airflow, etc). It basically turns into a fluid thermodynamics modelling problem, which I'm not even going to try and attempt here. If you're serious about developing and verifying such a setup, you will need to verify it experimentally yourself.
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