I can't speak for OP, but some people sleep through alarms if they haven't slept enough. My oldest will legit just sleep through his phone alarm if it has been less than 5 hours since he went to bed. I've just heard his alarm go off in his room for 20 minutes straight before I walk in there and shake him awake. Shit is a problem.
I am assuming he won't be able to go to bed at a decent time. I wake up at 6:30am most days and I know I couldn't go to bed at 6:30pm. If he woke up at 3pm, it would be a tall order to fall asleep before ~4am I'd figure. Which gives him ~3 hours of sleep.
I think OP's major problem will be falling asleep again (given how late it is) to then be able to wake up on time with enough sleep to function through the day.
And, from my experience, sleep (or better: your desire to fall asleep or ability to wake up at specific time) does not correlate to tiredness. Sure, there is some dependency on that, but it's just one of the factors.
Sleeping over alarms? That's easy to fix. One should attach an electrode to his body and charge the capacitor on the other end of the wire. The capacitor is powered by a battery on one side, just to keep the capacitor charged. Then, in the middle of the wire, there's a relay/transistor that passes current at 3AM, the control signal is sent by an Arduino or something else with a clock. It will pass through the body a short electrostatic discharge needed to shock the body that would be painful but not causing any injury.
Not an electrician. This may be useful, but without warranty.