Hey Hun, I agree with katie that this looks like discomfort is at least in part messing with sleep. 20 min WU for us were always discomfort, and 30-40 was Ut/OT or sometimes also discomfort.
Does your LO have a dummy?
When are you giving the omeprazole? - is it in granule form (open up the capsules and pour in?)
I wonder if you would be best to stop the solids and see if it helps....solids can sometimes be great for refluxers, but sometimes it messes them up
Have you got your LO on probiotics? - they will help with the tummy trouble too, and are good for the gut during the time he is in meds and while his digestive system is maturing.
I wouldnt worry about APOP at the moment. He's OT but you can't do much in the way of st right now anyway so I would aim for one nap in the cot if possible. If you get 20 mins try to resettle in your arms if you can - at the moment you all just need some sleep
One thing I do wonder is if he needs a higher A time just to start with to get him tired enough for a good morning nap. Again, even if it ends up in your arms, on a recliner, wrap or pram, car, etc for some ,or all of it. At 5 mths my touchy ds1 needed at least 2.5-2hrs45 after his night to get a good nap. His As got shorter throughout the day