I am remodeling the second floor of my house consisting of 2 bedrooms, two baths and associated closets, about 800sf.  I would like to incorporate radiant hydronic floor heat.  The house is now heated with a heat pump.  The heat source for the radiant would be a wood fired bake oven in my back yard.  I have 20 linear feet of 3/4 copper pipe running above the firebox of the oven, then piped with 3/4" PEX through(heat exchange) four 55 gallon drums filled with water for heat storage.  The PEX runs insulated undergroud for 30 feet to the
house where it then goes up about 12 feet to the second floor in an insulated chase where there will be a 4 zone manifold.  The PEX will change to 1/2" at the manifold.  (This is a closed loop system) My first question is how do I size the pump?  Can I get by with one pump?  Since the first floor is also an interior heated space, is it necessary to insulate the upstairs floor?  I would also like to put radiators in two rooms on the first floor close to where the PEX runs.  Since radiators use a hotter water, should the PEX from the heat source run directly to the radiators first and then to the manifold?
 Bake ovens can get as hot as a 7 or 800 degrees.  I realize that PEX is rated at 180 Degrees.  I am hoping that a two inch layer of perlite insulation between the firebox and the copper and the four 55 gal drums of water will cool the water to a usable temperature.  I am planning on small fires at first with temp gauges throughout to understand the characteristics before I trust it.  If people feel uncomfortable answering these questions because of the unconventional heat source please refer me to others who are in the know.  Thank You!