First of all, the situation you describe is very common. The hours between dinner and bedtime include some of the most stressful moments of the day. It's hard to accomplish all that you need to do, and get the kids to bed "on time." However, your son's behavior may suggest that he needs more sleep than he's currently getting.
The American Academy of Pediatrics Guide to Your Child's Sleep provides some helpful guidelines regarding just how much sleep children need at different stages in their development. Keep in mind that these numbers reflect total sleep hours in a 24-hour period. So if your son still naps, you'll need to take that into account when you add up his typical sleep hours.
Between Birth-Six Months, children need 16-20 hours
Between Six-Twelve Months, children need 14-15 hours
Between Ages 1-3, children need 10-13 hours
Between Ages 3-10, children need 10-12 hours
Between Ages 11-12, children need about 10 hours
Teenagers need about 9 hours of sleep per night
If those numbers are surprising, you're not alone. Single moms and dads, especially, are often forced to get by on 5, 6, or even fewer hours of sleep a night. As a result, it might be tempting to think that your kids can also get by with less sleep than they need, or that they should be able to cope fairly well with a few skipped hours here and there. However, kids who are regularly sleep deprived will exhibit some pretty difficult behaviors. They display frequent irritability, overreact emotionally, have difficulty concentrating, forget easily, wake often during the night, and may even display hyperactive behaviors.
The best thing you can do is simply move your child's bedtime up. This may sound impossible at first, but by moving his entire bedtime routine up half an hour, you'll help him associate bedtime with an earlier time. In fact, you may be surprised to find that he goes to sleep more easily and sleeps through the night more regularly when he is well-rested.
Cohen, George J., M.D., F.A.A.P. (Ed.). (1999). American Academy of Pediatrics Guide to Your Childs Sleep. New York: Villard.