How to properly terminate this circuit
You will more-than-likely get away with scenario 1 but if you were to be picky you would terminate in 52.63 ohms: -



52.63 || 1000 = 50.

Nearest value to 52.63 ohms is 52.3 ohms and this, in parallel with 1 kohm gives 49.7 ohms i.e. 0.5% away from perfection.