I wonder if you are doing what we are doing? As soon as DD makes a peep, we are in her room patting her so she stays asleep. I think this sometimes makes her more awake, rather than letting her try to self-settle. We were up this morning from 4.30am until about 6.00am trying to settle her back, in the end I said to DH, she isn't crying, just whinging so I will leave her alone. She self settled until about 7am. In the end I got her up and put her in bed with us and she slept until we woke her for her feed at 8am.
The other thing is, what time is the last night feed? Have you tried a dreamfeed/rollover feed? We just reintroduced this at 11pm and DD most of the time sleeps through until 7am-8am. Some children drop this feed, but maybe you DS still needs it?
It looks as though your DS can sleep and self settle during the day and you have a 'routine', so not sure why he won't do this same during the night. I have a suggested routine from a sleep school I went to, if you want me to PM or e-mail it to you.