To answer your first question, you could use the Formatted Numbers plugin available on the DataTables plugin page. I would post the code here, but since they update often, I'll just post the link instead.
http://datatables.net/plug-ins/type-detection
You have a couple of options for disabling sorting on a particular column. You could take the legacy route and put a line in your init object such as...
"aoColumns": [
null,null,null,{ "bSortable": false },null,null
]
Where null is a column you don't want to do anything to, and the bSortable object is the column you want to effect.
Since you are running 1.9+, you can do the following.
"aoColumnDefs": [
{ "bSortable": false, "aTargets": [ 4 ] }
],
In this example, 4 is the column you want to disable sorting on. Remember, the first column is 0, so this would technically be the 5th column.