Apart from being tired and snappy does he have any other behaviour problems.
If not need to start getting strict. All four of mine have done absolutely everything they can to avoid going to bed / going to sleep. I have various health conditions and if I don't sleep I get really ill therefore I've always been really strict about bedtime. Of course I try and push it but you just have to be consistently boring and repeatedly put them in bed.
I would make a big fuss about how he's going to be such a big boy now and is going to start going to sleep by himself. Tell everybody you're going to do this and make it sound like he is so cool for doing it. Get him excited about the idea and set up a start-up so that if he manages 7 days of it he gets some nominal treat. During the day away from the house set the ground rules with him.(ie short bedtime routine, read himself in bed, lights out 8pm. No leaving the room after this, no getting out of bed and no noise.)
On the first night when he inevitably keeps getting up just calmly tell him first time that it's bedtime and time to sleep and put him back in bed second time that it's bedtime and the third time and next 200 times say nothing just put him back in bed.
Do similar if he is shouting.
Then repeat this very boring routine for probably the next week. Repeat it in the middle of the night if necessary.
Make a massive fuss of him the next day again telling everybody.
Try and make out like it is a really good thing and that it is not a punishment but a reward for being such a grlwn up boy.
I know it's really hard my eldest has Aspergers and thus doesn't sleep well. But he learnt from a very young age to just lie in bed and read/ look at books.
Other things that made a difference were no screens after 6 p.m., and no more than an hour a day, loads of exercise, no stimulating food after 5 p.m. (sugar/ juice/squash etc).
This has worked with all four of them at various ages you just need to be consistent and strong. If for example on the 3rd night you give in a bit they will not forget that and persevere until you do so again.
It's very worth it to get your life back and also it's necessary for them to get enough sleep. I have friends with children that co sleep that are just all exhausted and they all snap at each other because of it. It's really not fair on the kids or the parents.