Elevation
I think you may need to re-read what P22 has written. Nowhere does it say that the rudder is blown to the right by the wind. P22 said, and meant, the fin. In a crosswind take off, on the vast majority of modern aircraft, the (outboard) upwind engine is the critical engine, for the reasons given.
P22
I also remember the B747-100/200 series being Vmcg certified only to a 7kt crosswind, with the correction to Vmcg being +1.33 kts per extra knot of crosswind. As was discussed in a previous thread, this could result in the actual Vmcg during a 27 kt crosswind take off being nearly 27 kts higher than the nominal Vmcg.
Once airborne, I think I would describe the downwind engine failure as requiring slightly more co-ordination (and therefore being slightly more difficult) rather than being critical, at least in the sense we use the word critical before Vr, meaning the ability to remain on the paved surface until either lift-off or coming to a halt.
From my observations in the B747 simulator over the years, any engine failure immediately after lift off was significantly more difficult, and rarely as well handled, as an engine failure immediately after V1.
mutt
The only reference I’ve got is my UK CAA Base Training notes for the B747, so I can’t provide the definitive source you seek, but from memory, that was the figure, and the correction, that was in use. I’d be the first to admit that this is not conclusive!