Hi, so sorry, Alison. I know how you feel.
We had the same thing with-my son. He's going to be 11 in Dec. and he's a lot better.
We never did any medications except for Adderal. Is he taking anything for his ADHD? I know a lot of people say to do the mood stabilizers or serotonin uptakes first, but we preferred to work with-the ADHD first and we got lucky, plus, we've worked very hard.
Now that I look back on it, I found that my son was picking up on my anxiety, because I was rushing around, yelling from room to room, "Everybody ready?" or "Got your shoes?" and while that's no big deal to me, it was and is a big deal to a difficult child. I had to pad every single thing with-at least 1/2 hr to an hr extra in regard to time. I resented it, but then when it came right down to it, I was wasting at least that much time with-his meltdowns and stubbornness.
I'm thinking your difficult child is picking up on your stress. You asked, "Why is it always the days when I have the most things to get done?" and it's no coincidence.
Don't take that as a slam. It's simply a suggestion, but I've noticed that our G'sfg overreact to absolutely everything.
In regard to his violence, I used to literally drag my difficult child out the door. I usually chose the front door, for various reasons. I told him to run around outside. He would try to fight me, but I was usually able to get him over the threshhold. This helped him as well as me, because his rages would often put me over the top and I didn't want to hurt him (overdoing it with-yelling, spanking etc.) We have nearly 4 acres, and I hoped he wouldn't choose to leave our 4 acres and whine at a neighbor's house (how humiliating--"my mom kicked me out!" LOL) but it never happened. He always stayed in the yard and I could see him from the windows. Now that I know the neighbors better, they would have all done the same thing with-their kids, LOL!
It sometimes allowed difficult child to calm down, but my problem was I always expected to speak with-him, either to get an apology or just to tell him to go to his room when he came back in.
Big mistake. It takes a long, long, time for a difficult child to truly calm down (sometimes overnight) so just because they aren't kicking and screaming at that moment doesn't mean they won't start up again in an instant. He would take ANY word from me as a signal to start fighting again.
Someone here (I have to dig up the note--it's a good one) said that one reason so many kids with-ADHD have ODD is because they crave the stimulation of arguing. Now, I'd want to think that it's much more enjoyable to be stimulated while rooting for my team at a game, or jogging around the block, but G'sfg use the easy, base instinct of anger.
You said, or implied, you're having a hard time keeping him in Time Out, which is his room. I had the exact same problem. One thing we did was reverse the lock on his door so we could lock him in. It saved our sanity.
Eventually, he broke it, but hey, you can always buy another one! At least he didn't break the hinges.
I had to race him to his room by telling him that the first person up there got their pick of anything on the floor--forever. Since the room is usually junked up, it's easy pickings. (That was the child psychiatric's idea.)
Then, once he's in there (the key is to let him rush past you at the last second, and he'll give you one, good, hard, last shove before he goes in) then you step back quickly and lock the door.
Sneaky, but effective.
Expect him to try to kick down the door.
Put in earplugs and get some work done. (Easier said than done!)
I would not call 911 on an 8-yr-old unless he had a weapon or had lived through some trauma where he had witnessed horrific violence and knew how to carry it through. IOW, most 8-yr-olds are not as adept at true violence as we would believe. Now, if you've got friends in the police dept., you can set up something where you call them to come over in uniform, but chances are, he won't be raging at the time. It's hard to make your friends' schedules mesh with-a tantrum!
Also, since he's saying "it's so hard to be good at school, it's hard to do it at home," you may want to reward him in some way each day he comes home calmly. Now, he may not remain calm all evening, but you can extend it day by day, for a few min. at a time. For example, "You've been really good at home, not annoying your brother, and not following me around. You can watch an extra 15 min. of TV right now." (or have a snack, etc.). Then, the next day, set a timer and tell him that if he can be good for an extra 15 min., he'll get an even bigger reward.
I used to worry that it was too much like training a seal, and it wouldn't help him develop a conscience, but most of these kids have delayed development so it's going to be a long way off. You have to work with-results, and then work backward as to the effects and "Why" of it all.
My son likes Reese's peanut butter cups (yes, he will take that over a $20 bill. LOL!) I also like to give him a break when he gets home, because if we go straight into homework, he really will have a meltdown. So maybe 1/2 hr of a calm, funny cartoon (we have a huge collection of Bugs Bunny, as opposed to Transformers or Yu-Gi-Oh or some inanely violent garbage), and then help him transistion to homework or some small task.
It means when you are home together, you will be lucky to get working periods of more than 15-min-1/2 hr, but it will lengthen over time. Also, consider that they will be calm periods, which helps considerably.
I don't know why he started his downward spiral but all you can do is not spiral down with-him.
Good luck!