The first measurement I took was connecting the op-amp input to GND.

Using the 16 k resistor instead of an ideal 16.666 k resistor gives an offset of ~59 LSB (I built another version with lower input impedance, i.e., RS 3k, RM 750, RT 1k, RF 430 and RG 270, and the offset is not there).  There is also some ~21 MHz noise.

Next measurement was the 3.3V supply.

Next, I made a PIO state machine that would output a simple 16 bit pattern: 1011 0111 0100 0100.  Then, I set the PIO to run at different frequencies.  Here is the view of an 8 Mbps signal:

Here is a view of a 24 Mbps signal:

Here is a view of a 32 Mbps signal (getting a little dicey!):