We see that the column structure is still visible but the regional drift is mostly gone. The "U" shape might be due to the linear correction, whilst at least a second order correction would most likely be required.
However, the regional effects are now in size close to the column effects. The plot of pixel values against gains shows a single band without the drift.
Quantitatively we are in the range of the noise and in principle it doesn't make sense to continue. It would be nice, though, to do a beautification and level out the column noise, to remove the visible effects, which now are already much less visible than before.
To be continued...
P.S.: I also looked at the coarse map (3rd image), which I assume to be the pedestals. They don't show any remarkable structure, so I assume it's save to ignore them.