S210 drive and 1FK2 servo continuous operation ?

Kindly, can we use the S210 drive and 1FK2 servo for a continuous operation ? 

(with less then 50% current consumption)

Of course you can also use an S210 with 1FK2 in continuous operation. 

I recommend to use the offline version of the TIA Selection Tool - here you can define your load profile and you will get the correct sized motor and drive.

Can also the  S7-1500T + S210 + 1FK2  work well to do Synchronous Gearing / Cam Profile / ... ?

Yes, for sure it can. That is exaclty 100% the use case which the S210 and S7-1500T was designed for ;)

The S210 is meant to be a very fast servo drive that should be operated by the 1500 PLC