Mohammed
1. When in the wait mode the processor 's core will be 'frozen', therefore you can do anything like checking registers. The simplest method is to set a break point after the wfi instruction and if it is hit it means that it has "woken" again.
2. The WAIT state is existed when there are interrupts pending "before the mask" so it is normal and correct to globally disable interrupts before executing the wfi instruction - this will have no effect on the wake-up.
Check also http://www.utasker.com/kinetis/FRDM-KEAZ64Q64.html - the binary there probably has low power tests according to http://www.utasker.com/kinetis/LLWU.html
Regards
Mark