Hi there, thanks for the detailed EASY! Just a few thoughts to ponder...
That looks like a great first nap, I wonder how he would respond to stretching that first A time just a tiny bit, to get the nap closer to 2h? May not be necessary, but it may help to push the day out a bit without him getting OT...
I'd be surprised if the second nap was UT, given that he had such a good first nap on a shorter A time, but perhaps he was just more refreshed after his long nap? You could try pushing the second A if you really think it was UT, but it could just as well have been OT... I wouldn't push both first and second As at the same time though, so pick one and see what happens.
If you do get a short second nap, I would definitely reign in the next A time, I reckon he would have been OT by the time of the third nap and certainly by BT. At this age, mine would often short nap either of the first two naps (or both!) and take a longer third nap, instead of a CN, and that was fine for them, since they needed it to make up for the earlier short naps. I think you want to try to avoid OT at BT, I'd have probably gone for the third nap no more than 2h after the previous short nap, and let him sleep a little longer. That 1.5h stretch at the beginning of the night is typical of an OT LO, as is the early waking and struggling to settle afterwards. I know it sounds strange, but often letting them have an early BT can help them to catch up after short naps and result in them actually sleeping better and night and waking later too.
As for the BF - do discuss with a lactation consultant or doctor if you think the reflux is bothering him still, they could watch you feed him and see if he seems uncomfortable, or whether it's just his normal feeding patterns. Please be aware that here on BW forums, we tend to feel that Tracy's BF guidance is a little outdated in the light of recent studies, and that she would probably have updated them if she were still alive now. I'd still encourage you to see if he'll take longer feeds during the day, by making sure he's burping if necessary, comfortable, not distracted, etc, have you offered both sides... But be aware that you may just be a nursing pair who needs to feed a bit more often, perhaps due to the reflux, or small tummy, or lower than average milk storage capacity of your breasts - there's actually a huge range! If he's content and satisfied after each feeding and definitely doesn't want more, then rest assured that many, many LOs never 'make it' to 4h until solids are well established, and some mums will 'top up' just before a nap to ensure their LOs don't short nap due to hunger, whilst others will give a top up around an hour after the first feed, as it seems you're doing already. I certainly wouldn't want to be weaning any daytime feeds just yet, although it may be that he'll 'consolidate' two into one (during the same A) - or he may not. But I mostly just want to encourage you to continue to tune in to the cues your LO is giving you, and don't feel pressurised into trying to stretch his feeds apart if that's not what he needs
I'm hoping that if he's less OT at BT, then he'll become more settled at night, and then you may be less worried about feeding him, knowing he'll settle again afterwards. It's pretty normal for a 5mo to need two bfs at night.