Pump Control within Efficiency Curve

Hello Forum,

I am developing a Pump Control System and one of the most important modes of operation, is to keep the Pump operating inside it's efficiency curve range. As seen in the picture below, the chart represents the Pump's efficiency curves at different operating frequencies and the one I have highlighted is the 60Hz curve which is the most ideal. The circle on that curve is the Best Efficiency Point and the Control System needs to target that. X-Axis is Flow and Y-Axis is Pressure.

I created a limiting block that defines upper and lower limits for both Flow and Pressure and at the moment the only way to stop the Pump from operating at Max Flow limit, I created a "Power Limit" block which goes closer to 0 when the Pump's Flow is reaching the higher Limit and thus slows down the Pump's speed.
So, the Pump is operating at 100% of allowed speed until it reaches the Max Limit on the flow in that frequency range but I need to keep it operating between Min and Max limit while trying to achieve Best Efficiency Point. I can limit it from hitting Upper Limit with my "Power Limit" block but I just wanted to ask your suggestions as to what would be the best way to take this logic forward and have the Pump
(a) Keep operating between the Lower and Higher limits for both Flow and Pressure
(b) Target Best Efficiency Point when running at 60Hz frequency.

Keep in mind there is Pump's Speed to Control and also Control Valve Position to obtain maximum safe performance.