Is my mixed signal PCB Layout correct for EMC and Signal integrity( pic attached) ?

[vipinsaklani]

Dear All, I am designing a mixed-signal PCB for my upcoming project. It acquires a weak analog signal and processes this with an FPGA before giving out serial data. This is my second board. While my first bord with the same design was functional, its noise performance wasn't good. I was losing out on the resolution of output data. I am attaching the pic for you folks to find out any mistakes in the placement of different components and proposed layout.

I have the following queries:

1. Is my stack up well planned? My earlier board had only one ground plane but now I am planning to pour copper on all the layers and connect all of them with vias.
2. My earlier board had a break in the ground plane and the bridge was placed directly under ADC ( I did not have digiPOT and DAC then). I am planning to have a solid ground plane now?
3. Is the placement of my connectors OK?
4. Which side of the ground plane, should I put my input supply connector?
6. How should I connect the coaxial signal cable's ground to OP-AMP? If I connect it to the ground plane ( Like I earlier did, will it degrade the analog signal )?
7. As OP-AMP does not have a ground pin, how the return path of the input signal current is traced?

Any suggestion is welcome. Thanks