I like most of your ideas, but I don't understand why you want to seal your wall studs to your sheathing. I think that you can accomplish more by ensuring that your housewrap (Tyvek, Typar) is installed carefully and completely. There is a companion product, tape, (Tuck tape, mfg. name, red in colour) that is used to seal all seams and perforations, including windows.
To seal and insulate you windows to your studs I would recommend "low E", low expansion spray foam. Low expansion foam will not put pressure on your window and door frames, warping them. Trim any housewrap in the stud openings back to expose bare stud, so that the foam will bond to both surfaces.
The sealant that I use for most vapour barrier issues is "Acoustical Sealant", it stay soft and flexible, allows the house to settle without failing. Beware of it though, neatness is important, it can quickly cause a sticky mess.
The light cans, glad you brought this up. This is an item that can render all your other efforts useless. Be SURE that they are VAPOUR tight- look for the compliance label. There is a different grade- "insulation safe", these are not necessarily vapour tight, they are designed to be safe if insulation is installed against them, but, often air can travel through them.
If you are installing a conduit through to the attic, why not install two? A second pipe would be handy for an AC circuit, such as an attic fan, power vent or whatever.
Lastly, when your heating ductwork is installed seal the boots to the subfloor with aluminum foil tape. Probably the most important factor here is the workmanship of the ductwork guy- the better the fit between the boot and plywood the better. Once I watched a guy cut the holes with a chainsaw. It was a nightmare trying to fix that one.
Good luck! And keep us posted!
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