Hi there and welcome to BW

First, please please don't feel guilty, everything you have done is in an attempt to do the right thing for your baby and your family. all of us here have been lost at some point, and sleep deprived too. It's exhausting!
It sounds to me like you know exactly how to reassure and settle him, if this means picking up then do it, it's fine. Yes at this age usually the advice is just to lay them back down, so jut the PD part of PUPD but if he finds it more reassuring to have a PU and if you can manage that (he sounds heavy) then do so. Mine also always needed a PU and a cuddle before he could settle, it was often very quick but not always, I gave what he needed and discovered he always asked for only what he needed and no more. Respond to all his cries/shouting/frustration calmly and supportively, he will likely be very frustrated by the changes and will need all your support to help him through, it may appear that you being there with him makes no difference (because it doesn't stop him shouting and crying) but it does make a huge huge difference, he knows you are there and supporting him, it is totally the opposite of CIO. So, yes, pick up if needed, use just a hand when you feel this is enough or the right time, just the way you have learned.
If your LO has a lovey he might find it comforting to have this during cuddles and sleep time to help him self settle without the bottle. If not, this might be a good time to introduce one, I use a muslin square, it was with us every feed, every cuddle, every sleep (when very little I didn't let him sleep with it), it has incredible power to help LO fee reassured. Mine still uses his now and he is almost 5yo, he also takes a little mini one to school in his pocket to give him extra reassurance at school (looks much the same as a handkerchief). The benefit of using a muslin is that they are plentiful and washable. Just an idea for you.
WRT the feeds. Can I just check, is there a WU milk? Not sure if you've dropped that milk feed due to solids breakfast coming at 8am or if you forgot to put it in your EASY times.
Is he eating his solids meals well and does he get a fair amount of protein and fats?
Have you tried dinner earlier, maybe when he wakes from that second nap? Many babies eat better earlier in the day and tend not to eat less if the solids comes later, so there might be a chance of him taking a bit more if the meal was earlier, also it might give him more time to digest and make room for a really good BT milk before he goes down for the night.
I know you are preparing for some long nights - try to plan for someone (DH?) to mind baby in the day so you can get some rest, making changes like night feed to sleep props can be hard work but usually are done in about 3 days.
Sending you lots of support.