Can the mass flow rate for different power settings be determined?
Yes, it can be done but you need a complicated model with information only the producer has access to. The data in your source are not enough.

You can play around with this a bit https://www.grc.nasa.gov/www/k-12/airplane/ngnsim.html but don't expect overly realistic answers. You have to use the Tunnel Test Mode for off-design performance after entering all the data you have available. And you should pick the "turbofan" engine type.