I simulated my circuit in LTSpice, as the spectrum analyzer I placed 50 ohm resistors. It works fine.
You would at least need an amplifier with a THD of -72 dBc at fin= 5 MHz, a much faster op amp would do so. Here are the possible choices: LTC6268/LTC6269, and ADA4857. Take note that ADA4857 runs at 5V and LTC6268/9 can run at 3.3 V. Also, reconsider your design. LTM9008-14 is specified to accept a differential input voltage of 2 Vpp. In your current schematic, you're running it at 4.8 Vp-p differential.