I don't think I have much advice on day to day stuff either. I second the call to Early Intervention. It's free and might be a real help.
Several books to look at (your library should have them or be able to get them for you):Kids, Parents and Power Struggles
by Mary Sheedy KurcinkaRaising Your Spirited Child
by Mary Sheedy Kurcinka (she's got a lot of experience in this area!)
I'd also recommend: The Out of Sync Child
-- sometimes these oppositional kinds of things result from sensory overload -- and a child with this needs different treatment. The screaming in particular is what makes me suspect this, though I could be way off.
Practically speaking I would:
1. Quit trying to potty train. Trust that she will not go to Kindergarten in diapers. My nephew (also a very strong willed child) REFUSED to potty train until he was about 4. Then, overnight, he decided not to wear diapers, andhe was trained. End of story. Right now, this is just one battle too many for you. Ditto for the picking up, ditto for going out to eat.
2. Stop time outs (they aren't working, they're just getting you hurt). Instead, work on finding a 'calming down'p spot. Don't try to enforce an amount of time. Talk to her about what helps her calm down, and maybe have her help set it up (at a time when she's not upset). Maybe a corner of her room with pillows and stuffed animals (soft things that she can't hurt you with if she throws them.) When she starts to hurt you, walk away. Tell her you'll be glad to cuddle, but you don't want to be hurt. It's a natural consequence of hurting someone that they don't want to be with you. I don't view this as love withdrawal, it's safety. You don't have to go far, just out of harms way.
3. When she has a tantrum, sit close by, but do not try to talk her out of it. Tell her you're there if she needs it, but don't try to hold her, talk to her, etc. Our ds, when he was like this, simply got worse when we tried to talk to him or touch him. (He's my child with sensory issues.) It was simply too much stimulation. AFTER he'd gotten a bit out of his system, then he was ready for a cuddle.
4. Childproof to the maxmium. Again. And again. Prevention is really your best bet.
5. Take her OUTSIDE for AN HOUR or two EVERY MORNING. And every afternoon. Make sure she gets LOTS and LOTS of physical activity. Crafts are great, but they aren't physical enough for a lot of kids. Do crafts after you come in.
6. Whisper when she screams. She can't hear you if you whisper and she's screaming.
Good luck! It sounds like things are really tough and stressful for you right now, and dd is not making them any easier. You will get through this.