Getting him to nap is a nightmare, he fights sleep with a vengeance
Yes, sounds like a chronic over tiredness cycle.
First - feed feed feed. Most sleep issues this age can be solved with lots more frequent feeds and bigger feeds.
Second - make sleep frequent. I reasonable approximation would be regular cycles throughout the day (ie 7am-11pm) of
- Wake - note the time
- Feed
- Activity - awake happy time ends as soon as first grumble or after an hour of not grumpy at all. Awake time of 40-60 mins is a good average.
- Sleep - short naps of 20-40 mins are normal.
Wake up and start the cycle again. Repeat repeat repeat. This is a baby lead way to ensure frequent feeds and naps throughout the day.
Third - make sleep as easy as possible. Don't make it hard for baby to get to sleep (for fear of rods for your own back and whatnot). Make it easy. That usually involve movement, something to suck and parental comfort/reassurance.
I favour an independant sleeping ethos to a cosleeping ethos. Therefore my favour would be dummy to suck, bouncy chair/pushchair/car ride for movement and eye contact and patting for comfort and reassurance.
The cosleeping parenting ethos would embrace breast feeding to sleep, sling or rocking in arms for movement and holding/cuddling for reassurance and comfort.
It doesn't matter which route you favour. Just fully embrace it to do everything baby needs to get to sleep and stay asleep for as long as possible.