My dear dear dear NaviSprite, I just want to give you a massive hug, and sit you down with a cup of tea ... and ask how I can help!
I wish I knew you in real life, I think a lot of posters are probably thinking the same.
I have one comment on all of your posts, one criticism really, and just like certain other people have said, my criticism is well meant... but unlike certain other people, my criticism won’t hurt you, I promise.
But I do want to give you a tiny ticking off!
You are not being kind enough to yourself
I think you know rationally that you are doing really well, and that, having just been through an awful loss, that you need to be letting it impact on your daily routine, because, you will break down if you try and carry on going like some kind of automaton not changing a thing whilst your heart is breaking inside... let alone your body, as what about the physical impact of going through all this?
So it’s actually a really Healthy Sign that you are modulating your routine to take into account how you are feeling right now, and what you are able to do and not do. That shows you are being in touch with your emotions and well, with the reality of you right now. Which won’t be forever. It’s about getting through the day and the nights right now, and that’s enough. Well, that’s your Herculean task is what I mean by ‘enough’.
Please be so, so proud of yourself for doing what you are doing right now.
You are being amazing
It would be amazing to be just surviving through the next 5 minutes, 10 minutes, or an hour. Just to get through it at all is the hardest thing you’ll ever have to do, when you are lost in grief and shock and living through some of the darkest moments you’ll ever see in your life.
I know it’s hard when idiots are pecking round the edges demanding more of you, and being stupid fucking unfeeling idiots, but please hold on to the truth, that you are achieving more in what you are managing now, than those idiots will ever achieve.
But I think instead of giving yourself a medal for every minute you don’t break down,
inside you are holding yourself to some ridiculously impossibly high standard of ‘supreme mother of twins’ which was set by all those people who have never spent any time looking after twins!!! And that’s without adding a new house, and a lost baby so very few weeks ago.
So that’s my tiny telling off, that you are not realising how wonderful you are being, and you need to be just so kind and so very, very gentle with yourself right now.
And for many months more, give yourself a mental medal each time you do even the most basic of things, like... get any sleep, medal for you! get more than 3 hrs sleep, huge medal for you! Get out of bed, yup, that’ll be a medal for you.
That might sound kinda weird to someone who’s not experienced such a deep and traumatic loss, or to people with an inability to empathise.
I think that’s why some people react so badly to grief, like your awful PIL. They want to pretend it’s like a bout of flu, something that you get, and you go through and then it’s gone and you never speak of it again. Especially with baby’s I’m afraid, one or two generations ago that was the way people are told to behave, to minimise the loss, wipe it all away like nothing happened, and to ‘get back to normal’.
I think it’s extremely selfish & weak when other people try and pressure people who are grieving to ‘act normal’. Because it’s for themselves really, it’s for their own comfort and social ease. Ugh.
Anyway, I digress, it’s not your PIL who should be the focus, it’s you. And you, please be kind and gentle to yourself, and remind yourself how brilliant you are being every day. 
