You're making it hard work for yerself, John. Use Flat-top edging kerbs, or flags on edge, to act both as shuttering and provide the requisite upstand.
Lay the edging/f-o-e on a bed of concrete and haunch as you normally would, then allow to set for a couple of days before placing the ramp/landing concrete. Don't forget the fall on the landing to ensure water doesn't hang outside the doorway.
I think I have a drawing or a photo of this construction, somewhere - I'll have a mooch and see if I can find it for you.