PCB Ground Pour, Crosstalk and antennas
all lines are single ended (like UART, SPI, I²C, etc.) and may have transition times of 1~3 ns.


This is where you went wrong. I2C and UART run at a few MHz at the fastest. SPI can be run at maybe 10 MHz. There is no need for transition times as fast as 3 ns. You will save yourself a lot of grief by slowing these down. The easiest way to do it is to add series resistance at the drivers for the monodirectional schemes (UART, SPI). For I2C, you can increase the pull-up resistance to slow the rise times. To slow down the fall times, you'll have to just use a weaker driver (no purpose-built I2C device should produce fall times this fast anyway).


  What I'd like to know, disregarding other routing considerations, is whether "fingers" A, B, D and E should be removed or perhaps they contribute to reducing crosstalk between the tracks.


Remove them.

They're only going to reduce crosstalk if you can find room to place vias into them to tie them to the ground plane underneath them and keep them at 0 volts along their whole length. And even that is chancy. More distance between your tracks is a better way to reduce crosstalk.


  I'm concerned that ground noise could make those "fingers" good antennas and produce unwanted EMI.


Absolutely correct.