Hi M.,
Hope to maybe offer a few suggestions. You did not mention how many naps and for how long he may take them during the day. If he takes 2 naps maybe cutting one of the naps out to make him more tired at night. Or try keeping him up a little later than you normally would put him to bed.
If that is not the issue then, Maybe set up an evening ritual... for example... after dinner and clean up, maybe have the whole family take a relaxing evening walk (weather permitting of course)Or even play a family game (something tiring for him like Hullabaloo by Cranium)-or even just turn on the radio and have a family dance time. After walk/game/dance give him a nice warm tub and get him all comfortable. Then perhaps sit in a relaxing chair in a quiet room with him give him a nice warm bottle of milk (you can even add a few tsp of cereal to the milk if he will take that and you can sneak it in) And read him a book. Before putting him to sleep make sure he has a clean diaper and has given you a burp.
Try to tire him out as much as you can during the day. Some other things I actually STILL do with my children once I tuck them in is tell them in a soft voice It's sleepytime, and pretend to sprinkle "sleepy seeds" on them. In order to activate my special "sleepy seeds" I must kiss them on their foreheads, the bridge of their nose and give eye kisses on both eyes. This usually helps to get them to fall asleep almost instantly.
He may not need more than one nap a day, or he could be having growth spurts. I have noticed with EACH of my kids that when growth spurts would happen my nightly sleeps or lack there of would get interupted quite a bit. Ask your pediatrition if he/she can offer and other ideas to get him to sleep through the night. Could it maybe be discomfort from teething? You could also apply some teething gel or something before putting him down.
I also notice with my 4 month old, sometimes she will cry out in the middle of the night but when I check on her she is totally sleeping so I don't bother her and she continues to sleep. Another thing you can try is instead of feeding him when he wakes up cuddle him and maybe rock him back to sleep, he may have just had a bad dream and wants to make sure you are still around. I'm not sure how clingy he is with you... but my 5 yr old was this way when he was little and he was VERY clingy to me. Sometimes he just wanted to make sure I was still avail. to him. If he wakes up more than once a night try to not feed him one of those times... then gradually get rid of the next feeding. Another thing that it could be is habit. Kinda like having your internal alarm wake you up. Which is might be good to try to just cuddle and rock him instead of feeding, gradually cutting back on nightly feedings. I personally would check for a burp or perhaps a dirty diaper when he wakens, he may not even be hungry. My 4 month old little girl seems to always want her diaper changed, I always check that first then go for a burp, now sometimes yes they may want a feeding... but try checking other issues first. I would definately try to cut out at least one of the feedings if possible.
It may take awhile so don't get discouraged. But the sooner you teach him to get a good night's sleep the easier it will be on you! I completely understand how tough it can be. I have 3 myself, a 13 yr old, a 5 yr old and a 4 month old. It is definately a challenge when you have older children! Good luck!