i so understand. my son is 10 and ADHD, then I have a younger daughter that is 7 and not ADHD. She know's how to push her brothers buttons.
Sometimes I just have to walk outside and have a cig, just to calm my nerves.
I've seen this at my house too.
In addition to a reward for eating as BPQW suggested, reward for properly expressing her anger, disappointment, etc. I had to give my daughter different words to express her anger with her father. She would say things like she wanted to kill him; then I got her to say she wanted to sell him but was afraid she won't get much for him, and then she would laugh. Now she just tells him she is mad at him and to please leave her alone until she can calm down. (she doing much better at handling it)
Sorry, I just had to laugh at After he got them to bed, I yelled at dh some for not being able to control the situation ! I have SO done that!!
I think that it's probably a good idea to stick with the schedule. Sometimes we skip if I know we are just hanging out at home all day, and then gird my loins for a day of back-sass and arguments.
As far as food, could you divide her plate into zones and give a reward for eating a certain amount?
We all have days like yours.
I am trying some omegas along with his stimulant medication. I heard that the omegas help maintain a good mood so I thought it was worth a try. My DS has not been too crabby lately but I would say it is too soon to determine if the omegas are the case or not ( omegas are supposed to take 6 weekes to be effective). DD made me so mad yesterday. We took the kids out to breakfast yesterday at Cracker Barrel (they love that place). BTW--didn't give meds to dd because we wanted her to eat. Brought the Gameboy to keep her occupied. We all went to the table except for dd because she was hanging out in the shopping area looking around, so I took the liberty of ordering a chocolate milk for her. Of course, when she came to the table and saw it, she freaked out because she didn't order it. Crying, etc. Another waitress came by and started talking to her, and talked her out of ordering a root beer and into ordering a hot chocolate. Then dd was fine. She ended up drinking all her chocolate milk, and just eating the whipped cream on her hot chocolate.
She took her med after breakfast. Later that morning, dh took them to see a movie (Flicka). All is good. Their 3 friends came over after that and they played inside for a while doing arts and crafts and just hanging out. Then we sent them outside to play for a while because they were pretty loud and getting snippy with each other. They were having fun even though it was cold. All is still good.
It started getting dark, and dinner was ready. Didn't give her the afternoon booster because we wanted her to eat dinner. DD came in and immediately started having a meltdown. I made hot chocolate for the girls since it was so cold outside. She didn't want it, she wanted chocolate milk. She didn't want to try the lasagna. She was a major PITA. She was talking back, firing death looks at everybody. She got to sit on the stairs while the rest of us ate dinner. Then she ate alone. And she ate everything and liked it. 
Then comes bath time and she is just about always a PITA. Meds are usually out of her system by then. Last night she was yelling a lot and at one point telling dh "I'm going to kick your a$$". Well, I had had enough by then and went upstairs and spanked her.
I feel bad, but dh is letting her swear at him and it's happening more and more. After he got them to bed, I yelled at dh some for not being able to control the situation at bath and bedtime. So he came up with a sticker chart that he is going to use from now on. That's the good news. Hope it works out.
And I'm making a mental note to myself to keep her on her meds on schedule--1st thing in the morning, then at 3 in the afternoon no matter what. This ODD behavior just isn't worth it. I guess she'll be skinny.
I figure that is better than feeling unhappy and unloved because of bad behavior. 