So this is a stupid solution to a stupid code bumble, but I spent so long looking in the wrong places that I thought I'd make a post that hopefully people will find when they search for this error:
this.store has no properties
My problem was simply that I wasn't paying attention to the parameters required by the DojoData constructor.
constructor: function(inFields, inData, args){
Instead of:
var model = new dojox.grid.data.DojoData({
store:store,
rowsPerPage:dkp.pageSize,
