s-parameters are not defined @ 0.0000 Hz. They are defined in very low frequencies even in Hz range but not DC.
Adding s-parameters @2 frequencies into s2p file will not solve your problem. The simulator will do an extrapolation between 650 MHz and toward to DC and it will bring serious errors.
In order to obtain s-parameters of a device, bias the device properly and do s-parameters analysis between the frequencies which you're interested in and where the large signal model is still valid.
Transient simulations don't give you any small signal parameters of a device or a circuit. Learn something about it.
Also, due to discrete nature of s-parameters, transient simulations do not like them.