huge hugs- sounds like a difficult patch but you'll get through it
the BabyDens are more like old style play pens, here's Elliott (Mel) in his when he was 15 months:-
My mum made the buffer to go round the inside, he didn't get locked in there for long and generally just went in and out of it all day but I'd read him stories in there and put certain toys he really liked in there and when I needed somewhere safe to put him when the door went, the phone rang or I needed the loo I knew he was safe and unable to get out and he did like it. They're not cheap but you could always look on ebay. I think ours was worth it and we've now got the play tent top for it so that he uses it as an indoor house or den. You can also use the frame to rope off an area of a room as well by attaching a bracket to the wall- my parents used to do this when we went up to theirs for Xmas to make a bit of their otherwise non-baby safe room ok for him. My mum says that when my brother was crawling and trying to grab things that I (2 1/2 years older) was playing with I used to sit in a playpen and play with the lego etc while he ranged around the outside so I'm hoping it will have a long term use too.
With the feeding have you tried cluster feeding towards bedtime, or hungry baby formula? I guess you probably have but just in case...? Is she teething? Elliott always got incredibly grumpy when he was teething. He has just gone through a nasty patch of scratching me when he's angry. It took weeks but everytime he did it I clearly told him off and put him upstairs in his cot and gave him time out and then got him to apologise- finally I imposed sanctions of no fun colours in his bath at bedtime if he'd hurt me during the day and that seems to have done it. I don't think these would work with such a young baby but somehow you have to get the message across that hurting you is not acceptable and that it won't get her what she wants- or that there are other ways of expressing anger. I've been giving Elliott headbutting the sofa lessons as he gets very angry and just doesn't yet know what to do with the rage (a sofa is better than the floor!). I don't know your little girl well enough to suggest anything or accurately think back to when he was the same age but I would think putting her down immediately, walking away to a different part of the room yourself and making sure she has a safe place to be angry in (padded!) might help. Does she understand the concept of pain do you think? I know it took Mel a long time to be able to think about that and realize that he was hurting us.
Is she better when you're out? Can you take her for long walks to cool down when she's in this kind of mood? Have you tried playing soothing music- didn't work for us at home but classic FM often does the trick in the car when he's kicking off as he likes listening?
Sorry, I've probably not been much help- just trying to think of some things you can try....
Hope it gets better soon
+++
edit: sorry just saw your spd comment so long walks are out! Another suggestion- have you any friends or relations who could take her for you for a few hours a few times a week- especially if she's being like this. I doubt she'd do it to them and it might diffuse the situation. Mel has never hit, scratched or pushed anyone but me and is a little angel when out with others! He also got into the habit of enjoying watching me get angry about the scratching so in the end me shouting louder and louder at him did no good and just egged him on- when I just scooped him up calmly and put him somewhere to calm down (counting to 10 in my head so I didn't lose it!) then he lost interest quicker although it's very hard to remain cool when you're being hurt by them I know.