For issue #1, you could use the OnCheckBoxClick client side event handler, this event will be raise for each checked row. In your case, you will need to set the checked property to the old value if the row checker is disabled. Here is the snippet:

function wgTest_OnCheckBoxClick(controlId, tblName, colName, checkboxValue, originalCheckBoxValue)
{
	var wgTest = ISGetObject(controlId);

	var chkBoxElem = wgTest.LastChkBox;

	if (chkBoxElem.getAttribute("disabled") == true)
	    chkBoxElem.checked = originalCheckBoxValue;
	
	return true;
}

For issue #2, in the OnAfterInitualize client side event handler, you will need to retrieve the checkbox header element and set the display style to none. Here is the snippet:

function wgTest_OnAfterInitialize(controlId)
{
	var wgTest = ISGetObject(controlId);

	var headerElem = wgTest.RootTable.GetElement(WG40.COLHEADER, WG40.HTMLDIV);

	headerElem.getElementsByTagName('input')[0].style.display = "none";
	
	return true;
}

The snippet use index 0 for the input because the checkbox is the first column in the WebGrid.