1) I personally don't think 2 spots is enough for ED injections. I do 2XW and I rotate 4 locations.
2) 1" in most cases isn't long enough for glutes. Seems like the typical rule of thumb is 1.5" for glutes, 1" for delts/quads/etc. How lean you are matters.
3) Oils... Yes. Oils & water based? I've never done it, but I've heard mix reviews.