How to find input impedance of RA30H1317M1 RF power amplifier module?
The test block diagram show input matched into 50 ohms, and electrical spec says input match is better then 3:1, so it seems likely that things input is specified to be somewhere in the 3:1 circle around a nominal 50 ohms restive. 

Note that full shout is specified at 50mW input, meaning your driver is good for ~10dB more then you need, personally I would pick a smaller driver stage, it will reduce your power consumption, the final is not linear anyway so IMD is not a concern. 

Some pad at the input is not a horrible thing, maybe 3dB or so at a nominal 50 ohms, it helps with stability. 
A BPF at the input is usually pretty nasty unless you know what you are doing, you do not want the filter output to go high Z where the amp still has gain or it will honk.