Yup, that's the one. I think the route is bring the wire to the frame with the rear brake hose then cross over to non-drive under the downtube to get into that hole.
Yep - that's what I've done and looks pretty neat. Put some heat shrink around the hydraulic hose and the di2 cable together, then just split near the join. I've twisted the di2 grommet upwards, and it seems pretty tidy in place.
do you not have a hole like the picture in this post