Hi there, wow you have a lot going on and congrats on the arrival of DS2 that must’ve been super stressful.
For DS1 there is so much going on, new room, potty training and new brother, I think when I had DS2 someone said to me your first has just had his whole world crashed around him. His mummy and daddy were his world and him centre of attention so it’s bound to have a knock on and then of course with the early labour and you being away will have crashed his world. (Made me so sad to think my DS1 was suffering) but they do come round.
Have you managed to do any 1 on 1 time with him, I know for us the first few months of mummy and him time were so crucial for him, we’d go out for a cake or to buy a magazine or the cinema just for a couple of hours I was totally his world again.
Also you could try capping the nap to 20 mins, I found this was just enough to see us through to bed and then shortly after dropped the nap totally. When you say you dropped the nap and did BT 6pm and WU was 6am that’s pretty good and normal, sometimes it can lengthen but on average a 12 hour night is good and of course as they get used to no nap you can push BT out by 15 mins d try few night to get back to 7-7 if that’s your chosen time x