Crystal filter impedance matchin
ECS-45K20A 45MHz IF filter - it has specified terminating impedance 910 Ohm / 2.5pF


Good question on assumption #1 which leads to #2.   

Rt tolerance animation on web shows 50 Ohm equip. + 1500 rather than +1450=1500 Ohm.   Yet datasheet does not show that.

So, I assume Rt includes 50 Ohms or any other voltage source or load value. 



Since the filter has internal impedance of 910 Ohms, an interstage R is not needed, just C to tune up the skirts e.g. BW @ -15 dB 

Note dot orientation.