Insulating/encapsulating crawlspace with HVAC ducting questions
Should I remove all the old batting and sheeting if the material is
  dry if I plan on encapsulating and insulating the walls of the
  crawlspace and close off the vents?


Yes.  Any and all fiberglass bat insulation should be removed.


  Mold does not appear to be a significant issue but would fogging the space while its still unoccupied be a good idea?


I would have the space inspected by a qualified mold remediation specialist.


  Is a vapor barrier with 10mil sheeting be sufficient and can I lay
  this on top of the old sheeting (basically addition underlayment) and
  up the walls?


10 mil vapor barrier is fine.  As to whether you can lay it on top of the existing vapor barrier, opinions differ.  I think that's OK (in fact am thinking about taking that approach myself), but only if there is no possibility of water getting into the crawlspace (pipe leak, from outside, up from the ground) that could then get get between the layers of plastic and just sit there.  If you can't ensure that going forward, then you need to remove the existing vapor barrier.


  Is insulation necessary on the ground?


No, though I have seen where some installers do that.


  Once the space is encapsulated and insulated does the ducting also
  need to be insulated?


Yes, so as to reduce the amount of heat loss from the ducts into a 50 deg crawlspace. 


  I plan on beefing up the sealing with foil tape and mastic but do I
  need to wrap as well or would I be better off beefing up the
  wall/floor insulation?


The crawlspace walls should be insulated with foam board and a vapor barrier installed.  No insulation under the floor.


  ...if any of the steps I outlined above in anticipation of this
  upgrade?


You would need to make sure a source of fresh air is provided to the furnace.  And, of course, need to vent the furnace exhaust to the outside.