Can hypomania/grumpiness occur with decreased sleep?

Yes it can.: Yes, sleep deprivation can cause both irritability and mild euphoria. Studies show decreased sleep increases the amount of Dopamine in the brain, promoting an amphetamine like response. This wakefulness comes with a decrease in the brain's processing ability. Sleep loss is also associated with increased appetite, risk of stroke, and heart disease.

Yes: Everyone needs at least 7 hrs of sleep, less may affect your health.