Reaching My Stress Limit...

I can keep my head in almost any situation.  I've been told all my life that I have alot of patience.  But life at home has worn me thin.  I am seriously at the point where I feel like my head is going to explode.
 
Marlow is cutting her third tooth, an eye tooth, and she is ridiculously cranky.  She screams if she falls, she screams if a toy doesn't do what she wants, she screams if she gets in trouble, she screams for the hell of it!  She won't eat, barely sleeps.  That means I am getting three hours a night of sleep, plus, attempting for almost two hours every meal time to get food into her.  She won't listen.  She has been hitting the dogs lately and throwing toys in people's faces.
Plus, I watch my nephew, currently for free when I can't afford it, to help my little sister out.  He's whiney, picky and mean.  He's only three months older then Mar but acts younger.  I was told this week I was needed only 1130am til 230am.  Well, yesterday and today he was dropped off at 10, and yesterday he wasn't picked up until 330!  Who knows about today.  What if I had appointments??  It makes me mad too.  I'm doing this to help, since I can't find a job.  And they will start paying me if her lazy excuse for a boyfriend ever gets a job, but until then I feed him with our food.  Her boyfriend never packs him milk, so I use ours.  Or wipes, so I use ours.
 
But that's not the worst.
 
Joey is the worst.  Seriously.  I don't know what's gotten into him lately!  We had a talk a month or so ago and I told him he had to shape up or I was gonna take Marlow and ship out.  I was tired of being walked on.  He got better, until I couldn't find a job.  Now he's even more of an ass.  And since my threat to leave is unrealistic unless I get some income he has stopped helping me. 
I need a break from Marlow, and he always says 'here, I'll give you a break' and he takes her out of the room for ten minutes then deposits her back with me.  Plus, he will not clean up after himself.  I mean seriously, he's 25!  Last night he made cookies, fine, whatever.  I had my workout class so I'm gone for two hours.  In that time all he really has to do is put Marlow to bed.  But apparently that takes so much work that he can't do a single other thing.  I came home from workout and went to bed, I didn't go into the kitchen.  But I did this morning.  Who the hell wants to wake up to that!  He had cookie dough stuck to the counter, two dirty pans, Marlow's highchair tray that I had asked him to wipe off was sitting on the counter with beans dried on it and a spoon with cookie dough stuck to it.  There were dishes in the sink, crumbs on the floor.  The dishwasher was clean, but he couldn't be bothered to empty it and reload it.  And when I get up he's already at work, and I can't leave it like that.  Plus, when I get home, tired because I just worked out, the living room is always covered in Marlow's toys.  It's a five minute clean up job.  Usually there is dirty laundry slung around the house as he lets her get into anything she wants. 
I'm so pissed off right now!  It's like having another child.  And when I confront him this afternoon, and I will, he will get all self righteous and angry.  Somehow blaming me.  My mum is coming over for supper and I have a cranky child, a soon to be cranky fiancee, and I'm cranky!  Seriously!!