I don't know how often the AIs make an offer in this version, but I'm likely to deny it anyway: I came to finish them.
I usually play with one ally and four enemies, if you team them up it becomes harder; with three teams in total there's decent variability in how they behave.
Yes.
At least that's my impression, I don't do SP myself.
Looking at the download numbers of the last entry in the dispute thread I don't get the feeling that it's inactive.
Title screen -> Learn to Play -> Tips and Tricks
or
binaries/data/mods/public/maps/tutorials/
The chevrons above the units' heads signify (from single to triple) basic, advanced and elite rank; they go along with increasing attack and HP values and decreasing gathering speeds. (Since this site's search function is phenomenally terrible I don't know if there's a good overview somewhere.)
The map has questionable "quirks", there's also "non-Terrain" more in the middle that one can usually not access and that hides even the silhouettes of units.