In-Law & MOO Situation: 4, 9, 11, 16, 18, 27, 41, 62, 69, 72, 86, 88, 89 (UPDATE)

Hi,
I hope it's okay that I post here as I know this is primarily a place for parents and DH and I don't have children. But we really need help.

Quick background for myself: my father unfortunately passed when I was little. My mother has been cut off for many many years after my realisation that I didn't actually have to accept being verbally, mentally and emotionally abused.
There had been times when tentative contact was made on my part however things very quickly reverted to the norm and, as I said, she has now been cut off for a very long time. She occasionally tries contact and it goes straight to the trash.

So. Onto the reason I'm here and I'm sorry if this gets horribly long.
DH and I married 5 years ago and since then we've both felt something just slightly 'off' with members of his family; me more than him. At this point I feel I should add that a few years ago I became disabled after a fairly horrific car accident and due to that have been unable to work. This, I feel was where things started to go wrong, especially when DH and I had periods where we had to sell pretty much everything we owned just to make rent and pay bills. It was a nightmare of a time, but it made us much stronger as a couple.

As our wedding approached, we discovered that his family members (aunts, etc...) were dropping out of the occasion like flies. Suddenly there was a new pet or someone needed a babysitter and it absolutely had to be that person, that kind is thing. During this time, we found out that my DH's (sort of) step-father (I say sort of as this guy, I'll call him R and my MIL aren't married but for all intents and purposes they are if that makes sense?) was actively looking for ways to get out of coming to the wedding.
R works abroad a lot and what he had been doing was asking for shifts to start the day before the wedding be because he really didn't want to be there. To this day, we have no idea why.
Wedding day was fairly uneventful, one of DH's brothers (J) gave him a flimsy excuse as to why he couldn't come down for it at the very last minute but we shoved that aside and tried to enjoy the day. Looking back at the pictures, most of DH's family looked miserable, especially his mother.

Not long after we married DH started noticing that his brothers only contacted him when they had nothing better to do. If he sent them a text or anything it would go without reply. So he decided to just step back and let them come to him, which never really happened.
We then began to notice that his mother was becoming a little distant (her and I had become close after my accident so this was out of the blue) and then a trend began forming: The worse my health got, the more the distance grew and eventually I asked my DH if he knew what was going on. He didn't, but had noticed something off and when we saw his mother next (she now lives abroad so we dont see her a lot anyway) he spoke to her and she denied anything being wrong with any of the family and then she changed the conversation.

So things carried on until one afternoon when DH's sister (S, who was in the process of moving back here to start college and is also a massive golden child*) used my laptop to check her Facebook and left it logged in and on a page of message between her and J's girlfriend (H) where they were joking and laughing about DH and I, the jist of which is:
H - so are you having loads of "fun" with your brother and her (I wasn't mentioned by name at all) there?
S - oh yeah...it's great...
H - sounds it lol is (MIL) enjoying it?
S - nah, she's says they're just really hard to live with haha
H - and she's right lol
S - yep
(At this point H had not met DH and I so how she could judge us is based only on what she's been told.)
So I took a screenshot and showed it to DH who was pretty pissed to be honest. As was I.
So we took some time away from all of them, not a cut off or time out but just some time for us to put all this together and work out how the hell we were going to talk to MIL about it all.

DH decides to send MIL an email. We figured that would be best because it would all be in writing and nobody could talk over him or try to make him feel like he was overreacting.

He lays it all out - how he's been feeling, how we've both been feeling and that we'd like to find a way forward from it but didn't know how and could we talk things out.
He reply was what I thought it would be: lots of talk about how much she's done for us, how hurt and upset she is, how could we think this, she thought we were close and that she's always considered me her second daughter, etc... No apology, nothing to open any line of communication about it at all.
So DH and I just left it. I know, stupid, trust me. I know.

So I'll skip forward to today and why I'm here taking your ears off.

MIL is here visiting for a few days. She's splitting her time between the family where we are and the family further up the country, which is usually the way it's done.
So her and S come over this afternoon and because S has acted pretty bratty in the past, we're both a bit fed up that she's tagging along but it's whatever.

Towards the end of the visit, S gives me her phone to look at because it's playing up and when I go to look at it, she's left it on a text message conversations between her and MIL that run a little something like this (not word for word here):
MIL - (some details about her flight) and then I'll have to visit DH and Mouse, shame ay lol
S - yaaay...at least you're not driving so they can't ask to go shopping (no freaking clue what this is about)
MIL - haha, very true she said something about them taking me for lunch, whatever that means
S - and where are they gonna go, probably somewhere in "walking distance" aha
MIL - yeah, but it's not happening

I screwed up and didn't find a way to show DH this in the moment. When they left, I burst into tears and told him and he just went into cold fury mode.
I asked what he wanted to do, how he wanted to handle it (figured that he should run this, considering it's his mother) and said whatever he wanted to do I would be behind him but that I really thought I was done. I couldn't take any more bitchy, two faced backstabbing. He said he totally understood and that the first thing he wanted to do was call MIL and ask her what on earth was going on.

So he did. He was really calm at first and asked her why her and S were doing this behind our backs and what we had done to deserve it. First of all she tried to make a joke out of it which just made DH angrier and he shut her down hard. He then moved on to the "walking distance" comments (keep in mind I'm in a wheelchair and I am really self-conscious about it, which she knows) and again she laughed it off and he blew his top. He didn't shout, but his words were to the effect of "you do not make jokes and comments like that about the woman I love, the woman I married" and when she tried to shrug it off further he replied with "I don't actually think this is f***ing funny". She then said that she couldn't talk to him right now and would call him later. His response was "to be frank I would really rather you didn't" and he hung up.

So that's about the it.
We would like to know where the hell we go from here.
If she comes back with an explanation and/or apology I've said that I can't continue as before because I'd know that the back-stabbing was still happening.

So, lovely people who have made it this far: I would welcome some advice. Friendly, please, I'm feeling horrible right now as I've not long come out of hospital.

Thank you,
Mouse.

(*basically DH is the oldest sibling and once old enough was free child care when not in school or work. His brothers and sister are all golden kids for various reasons, DH however is the forgotten one)
Edited because apparently I can't spell today and because paragraphs are not my friend....