The Si5351 looks cool and perhaps I'm missing something but banner specs for it says that the lowest frequency is 2.5kHz while requirements are 11Hz. You would need an extra output divider of 227:1 to get down to 11Hz but then your top frequency doesn't come close to the requirement of 11MHz. And we still don't know the expected resolution of the output frequency. 0.1Hz, 100Hz, 10kHz?