I assume you're giving him a milk feed at dinner time? I ask because there wasn't a mention of boob/bottle in your bedtime routine - maybe he's a bit hungry and might want a bit more milk at bedtime? If you're breastfeeding, breastmilk is designed to put babies to sleep so that can be an effective way to help facilitate sleep. Bottle-feeding can also induce sleep, with warm milk, sucking, cuddles in mummys arms.

The other thing I was thinking that maybe he's getting overtired - so I think you've answered your own question Perhaps bring the bedtime routine forward by half an hour or more, just see how he goes? Some babies are contented and will just fall asleep when tired, others need to be actively "put to sleep" before they get too tired, or else they are too tired to sleep, if that makes sense!

Sounds like a stressful situation for all involved, hope you can find a solution very soon *hugs*