My daughter had the same problem with alarm clocks. She could never wake up & slept right through the. Finally bought her some type of “sonic boom” clock. That didn’t work either. But the “sonic boom’ alarm also came with an attached vibrating pad that you put under your pillow to shake you awake. That worked & has proved quite useful now that she has roommates in college. She is shaken awake & the roommates sleep in.
Only way he wouldnt shut it off, and roll over and go back to sleep 😴.