Firstly I would suggest that 6am is not wake up time and is not breakfast time. It's a night wake. 11h sleep with one wake up sounds normal for this age. It so happens that your baby's night is 10pm-9am with a wake after 8h at 6am. In other households this could be an 8pm-7am night with a bottle around 4am.
Is there any reason bedtime is so late, since he's sleeping through for 8h? It sounds like you need proper sleep routine in the daytime, so I would use that as a time to change the night as well to 8pm ish and wake for a feed at 11pm ish. The hope is then that the 8h block of sleep is 11pm-7am.
As for your daytime, I think there's two things factoring in here. One is the timing of the naps. The other is the fact that baby will need more help to sleep in the day.
You don't really mention the timings of the naps you do at the moment, but I'd start a routine, it sounds like baby is ready for that structure given the 2h naps (when they do happen) and the long unbroken stretch at night.
A good example to follow for daytime naps at this stage is 234 (hours between sleeps). For example:
7am wake (wake baby at a set time every day, it established the rest of the routine)
2h awake time
9am nap (expect 1-2 hours)
3h awake time
1-2pm nap (expect around 2 hours)
4h awake time
8pm bedtime
11pm - wake for a feed. Wake properly with a nappy change. Then resettle with a feed. This should hopefully move the 8h block to 11pm-7am
(The timings of this can all be moved to suit. If a 10pm-9am day suits you better that is fine, just shift the timings accordingly and remember the 6am feed is a night wake, not morning).
With a more structured routine, it should help avoid getting into over tired territory. It is then a case of finding a method to get baby to sleep during the day.
The biology is such that the pressure to sleep is less in the day. Baby's body still needs naps, but it is more difficult for baby to get to sleep. So they often need extra help.
It sounds to be like crib naps in a dark room would suit your baby best for daytime naps. But you need to understand these won't be like night sleep, you will have to work harder to get baby to sleep.
The tried and tested easiest way, I think, would be:
- swaddle baby
- feed in cradle hold whilst swaddled
- lift to your shoulder and run back / wind. Sway a little as doing this, to get baby dozing.
- once calm on your shoulder, lay baby down in crib in dark room. Place your hand on baby's chest, over the swaddle, so baby can still feel your weight there
- if stirring have a dummy to hand, put dummy in. Gentle hold it in if needed. Stroke cheek to encourage comfort sucking and shushhhhh quietly as needed.
- stay there, hand on chest and keeping dummy in, completely motionless until dummy starts dropping out (when muscles go limp, mouth opens and dummy drops), slowly pull hand away.
- then sneek away ninja style.