Well my approach would be to work out a routine that you think will work for him, and make a start. I would suggest:
7am awake
12.30pm nap for 1.5hrs
2pm awake
8pm asleep for the night
This still represents pretty low sleep for his age. He may need more. He is probably quite unlikely to need less. It may be that times need tweaking as we go long.
So the main thing is the wind-down. 20 mins before sleep time make sure his tummy is nice and full, maybe a drink of milk here. Then take him into his bedroom and put on some quiet music and draw the curtains. Don't get hung up trying to get him to chill out, just sit quietly and let him do whatever. Then 10 mins before sleep time, do your wind-down routine (maybe change nappy, then cuddle him and do a little slow dance). Then 5 mins before sleep time, give him a kiss and put him in his cot. This is where he will start screaming and complaining. If he is happy and just playing in his cot, leave him to it and walk out the room.
Assuming he is screaming and crying, grab a couple of cushions and get comfortable on the floor next to his cot. Keep your voice low and calm, just tell him over and over 'lie down baby. It's just sleep time. Mummy's here.' Pat the mattress. Stay on the floor so that if he wants to be near you he has to lie down too. Maybe lie down yourself so that you're modelling the behaviour you want to see.
Expect this to go on for an hour. At nap times, after an hour, get him up, and then try again in another hour or so. It is quite normal for him to skip his nap entirely the first couple of days of sleep training - I'm telling you this so that you know it's normal and don't give up. If he doesn't nap, bedtime will need to be really early, maybe 6.30pm.
At bedtime, you don't stop after an hour - you just stay with him until he eventually sleeps. I would do alternate nights between you and DH, or you could tag team so you each do 45 mins and then swap. Do try to make sure that DH is involved at least half of the time.
This is going to be a real battle. Your little guy needs to learn how to go to sleep when YOU tell him it's sleep time, not to keep going like the energizer bunny until he crashes from sheer exhaustion. You will feel like he will cry forever, but he won't cry forever, he WILL sleep eventually, and each time he falls asleep in his cot, it will be easier for him the next time.
What do you think?