How best to fasten 30 pound range hood to wall - range hood has 2 large keyhole slots, I do not want to open the wall if possible. Would conical anchors (#12 screws) and construction adhesive be sufficient?
I'd be inclined to overengineer this; you can imagine that having a (greasy) range hood come down over a source of heat and/or flame would be bad.
What if you drill-and-cut new keyhole slots to match where your studs are? I think you should be able to fit two of them in a range hood.
Note that this is probably only an acceptable solution if the studs are reasonably centered on the range hood.