I've come to the conclusion that panic attacks and anxiety are extremely difficult for someone to understand, unless they've been there themselves.
Your husbands reaction of "you're being dramatic" is, sadly, very much a common one.
Mine used to (and still does!) tell me to "get a grip". It's not helpful in the slightest, but just put it down to lack of understanding, and nothing to do with you being weak or not coping.
Maybe you sleep better in your kids room because they're there with you? Maybe the lack of support from your husband makes you feel isolated, therefore you seek comfort and security from staying in the same room as your children? I have no idea, as it's such a complex subject, but these are just my initial thoughts .
With regards to your Mum, it sounds a bit 'OCD' to me... and I mean that in the nicest way possible.
I went for ages, having to do things a certain way at bedtime for fear of something bad happening to my kids.
I realise that sounds ridiculous, but it sounds very similar to what you're saying... every time you sleep in that room you think something is going to happen to your Mum, so you move. It then becomes a habit... which is extremely difficult to break.
I really feel for you.
As above, panic attacks are horrendous :-(