So both DS and DD will only settle for me. DD feeds to sleep so DH can't help there, and if he tries to put DS to bed it results in an instant tantrum that lasts for over an hour.

The problem is that DD is waking multiple times every night (about 4-6 times) and DS is waking 1-2 times. Because DD is resettled so often there are times when DS comes in to our room and I can't leave the baby to put him back to bed. So he just stands there and waits for me for 10-15 minutes (quietly and still as a statue, bless him). This results in:
a) if I get DD settled and then take DS to bed he is too awake to get back to sleep so I spend an hour in there with him, then DD wakes again and I have to go to her so DS cries, DD wakes = all up for the day at 3am
b) if I can't get DD back to sleep, hand her to DH and try to resettle DS but again he has been out of bed too long and is too awake = all up for the day at 3am
c) take DD with me to resettle DS, she wakes up, he wakes up = all up for the day at 3am

I have tried asking him to go back to bed and saying I will come in when DD is asleep but he just says "no thanks, I will just wait here for you mum".

I am not sure what to do! These 3am starts are hard going. DD will go back to bed around 6am for a couple of hours and DS will sometimes have a nap mid morning and sometimes he won't.

Probably not much point to this post, I am just totally over it!!