Usually when sapping and ballooning occurs with available host memory that is a sign that reservations are set incorrectly - do your have memory reservations set either at the VM level or Resource Pool level?
The discrepancy between guest OS memory and Active memory is two fold - remember that all memory in use by computer is being actively written or read from and the vmkernel also has technologies like Transparent Page Sharing to help economize on memory that the VM is using - the higher private/consumed memory also includes memory the vmkernel is using to mange the VM