I didn’t look at this carefully, just a general remark: you should stitch the front and back GND layers together with vias. Especially every sharp corner of a fill and then other corners and near all fill edges. It doesn’t hurt to have more than enough, there’s room for hundreds of vias. Like this. An arrow points to a place when you can move a track a little bit to fill more of the empty space.
All these vias give continuity for the GND copper. Otherwise you loose the benefit of copper pours because the current must find its way through longs paths. (EDIT: this depends on the frequency of the signals; see posts above which I read only afterwards. DC likes to find the shortest route. In any case it’s good to connect the front and back layer fills.) Without vias you also will have potential antennas, like here:
You can remove narrow antennas by moving some tracks closer together. In this case moving the front track above the GND slit (pad 4) downwards could even give room for more useful stitching vias.