Insulation, Radiant and Vapor Barriers - insulating a fixed attic stairwell

I have a fixed stair case leading from the master bedroom up into the attic. There is a temporary door (looks more like a garden gate - literally a couple of planks nailed together) at the bottom of the stairs which I have tried to insulate with tyvek panels cut to fit. Should I also consider some kind of zip-up attic seal to go over the opening in the attic floor (it's about 3' x 8' in total)? I'm guessing I'll need to replace the door with a proper internal door at some point, but any other suggestions?

Should I also consider trying to insulate the stairs themselves - maybe by lifting the stairs and spraying in some loose-fill, or removing the drywall panel from the underside and fitting in some fixed layers before refitting the drywall panel?

Id make a drop down door to fit that 3'X 8' at the top of the stairs say out of plywood and staple a R19 to it

Tyvek does not insulate. It is designed to allow air permeability and keep out moisture.

Attack the attic floor opeing as Ed says.

Dick