Hi there and welcome to BW
Sounds like you and he are doing really well, well done
My first thought was that for his first long nap, he goes down after 1.5h A time and has a good nap. But then he's up over 2.5h before his second nap, so he's probably overtired by that point and that is a common cause of short naps, which is what you're seeing. Can I suggest that you start by trying to push out that first nap a little? Perhaps keep him up a little longer so he has 1h45min awake before his first nap? He may still nap the same length on that or he may surprise you by taking a longer nap, you can let him have up to 2h. But then you can try offering the second nap earlier, perhaps at 1.5h like you have been for the first nap, or up to 1h45min if you prefer. We often find that whilst younger babies may give us reliable tired cues, older babies start being so much more interested in things around them that they may seem wide awake but actually be getting tired, and an OT LO has a harder time staying asleep. On the other hand, he may be rubbing his eyes like crazy after being up for 1.5h first thing, because his body is used to going to sleep at that time, but what he actually needs is a longer A time, so he can be ready to take a longer nap. Most 5mo LOs would actually be doing more like 2-2.5h A time, it varies greatly on the individual child, but I wonder if yours likes A times on the shorter side, given the good first nap you're currently getting. Does that make sense? Sorry, I feel I'm rambling!
The night waking may also be related to OT built up during the day, but as you say it's habitual, you might like to try using 'wake to sleep', have a read of this:
How do I address habitual wakings? (wake-to-sleep and other methods)Swaddling can be great during the newborn phase, but unfortunately it's not recommended once they can roll
So really I should advise you to wean that now, but there are some great products that can help with this - do you have sleeping bags at all? They're great for providing a feeling of snugness, avoid the issue of moving blankets and they can roll around safely in them
Can he roll from front to back? Although it's advised to always place babies on their backs to sleep, if they can get themselves on their tummies and roll back again themselves, you shouldn't need to worry about that. Not so with swaddled LOs as they can't use their arms to roll back again.