Jo - I have just seen this thread, and am really, really sorry for your terrible situation. At least you know that everyone on this board feels the same as you regarding Maci not being 'just a dog' and will sympathise with you having to seperate from her. Unfortunately we are considering emigrating at the moment, so it would not be fair for us to take Maci in as it would not be a stable home - but I really hope that you can find a resolution soon. I admire you for putting Maci first and toughing it out, despite you predicament, until you find somewhere safe for her.
Regarding your partner reporting her, why don't you try calling both your local police station and also your local dog warden to pre-empt the situation; I know the police are always keen to use the old 'we don't get involved in domestic situations' excuse, but at least if you at least had it noted that a) you were worried your partner may report Maci out of spite, and b) that he was be violent towards you hence there are extenuating circumstances for Maci to protect you, then at least that should stop him being able to report her and would be one weight off your mind.
Has Maci ever been to training classes (I know you have a baby and don't drive so this could be difficult for you)? I just thought that if she hasn't, then her dominance may be down to limited socialisation. If there are any classes near your folks, or even a trainer who could do a couple of one-on-one sessions, then perhaps your folks maybe willing to comprimise. i.e. say let you all move there on the understanding that you will go to training class, and if the situation with their dogs hasn't improved by the start of January then you will try to re-home her. There is a dog that started coming to one of our training classes 2 weeks ago and it was so aggressive towards every dog and just sat in the corner barking the whole class, shielded by a row of chairs, but one week later it just sat quietly, watching what was going on - so in such a short space of time it has made an amazing improvement. Something similar may be possible with Maci with the right help?
Our thoughts are with you, and hope that you find some resolution.