All your questions seem to be related to "How to get records on current page?"
you can extend pqGrid by adding a new function to get records on current page as below:
$.paramquery.pqGrid.prototype.getDataPage=function(){
return this.data;
}
For checkbox selections through header checkbox you may follow example code posted here
http://paramquery.com/forum/index.php?topic=376.0As you want to select checkboxes on current page rather than on all pages, you might need to use this modified code:
var data = $grid.pqGrid("getDataPage");
$(data).each(function (i, rowData) {
rowData["state"] = g_checked ? true : false;
$grid.pqGrid("selection", { type: 'row', method: (g_checked ? 'add' : 'remove'), rowIndx: i });
});