I also think that he might be ready for 1 nap, especially if he's up and playing for 2hrs in the morning (I believe Elmarie might have missunderstood your post & thought he was taking a 2hr nap
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You might want to try for a morning nap at around 10-10.30am (since most 17mo's can handle 3hrs in the morning) & if he falls asleep then great.... but wake him up about 30mins into the nap to preserve the afternoon nap OR if he's not asleep then you would want to aim for 1 nap but it would probably have to be earlier than 12.30-1pm.... & more like 12pm.
So on 2 nap days you would have something like this:
7am - wakes
b/n 10-10.30 - morning nap (30mins)
b/n 1.30-2pm - afternoon nap (about 1.5hrs long)
7.30-8pm - bedtime
The reason he is taking a long time to fall asleep in the morning is because he is not tired enough (so this is where you lay him down 1hr later).
The reason he might not be falling asleep in the afternoon is because he is too tired (awake for 5.5-6hrs for someone who is just at the start of the transition is long).
The reason he might not be falling asleep at night is because bedtime is too early... he doesn't need to be going down at 6.30pm if the afternoon nap ends at 4pm.
You could try 2 naps for a while or you could go cold turkey down to 1 nap... give him lunch around 11am & have him in the cot by 12pm. He might sleep for 2-2.5hrs & then you would have bedtime around 7pm
Edit to add - I also agree with Elmarie in that the 11pm bottle is not really necessary & its probably a good idea to start weaning it. You might have to do some wi/wo... at this age its more habit hunger than real hunger
hth
Layla