Alright well it sounds like to be honest you do know enough that you could figure out how to get off these if you tried. I think the main problem is your typical ADHD disorganisation compounding what would otherwise, perhaps, be a more manageable problem of just dosing too frequently, by losing track of what you've taken throughout the day. If you want to actually STOP using benzos, then your best bet, still, is to work out a taper plan and stick to it. I just did a quick google and found this (didn't want to link the site because I was concerned it was a bit too mainstream and maybe prohibition/total-abstinence leaning, maybe I'm wrong there but anyway:
So Step 1 is to figure out what dose of valium you need to be at a safe, comfortable place, not at real risk of seizure, and go from there. I just re-read your post and I see you mentioned you got Oxazepam instead, fair enough, if that's the accepted practice there I'm sure there's a good reason for it. Recreationally I always heard that oxazepam was pretty dull but that's not relevant here of course. The variety of substances you use with potencies I'm not familiar with means I can't tell you what dose would be a good starting one, there might be some trial and error but be safe and also don't give yourself a pass to dose higher than you need in the name of safety.
It's interesting you mention you have ADHD, I actually suspect I have that myself, I read Gabor Mate's "Scatterred Minds" which I would really recommend, if you're into reading and it really opened my eyes why I've found life such a struggle at times. I don't have the "H" component though, not really, my deficit is more being prone to prolonged vegetation in analysis paralysis whenever I have to organise my thoughts enough to make a plan and actually fucking do something useful. I experimented recently with self-medicating with Amphetamine Suphate, just recently finished it up following a few days where I used way above the recommended dose and sufferred for it. For sure it helps for focus but for me the negative effects are terrible. I often am driven to benzos in the aftermath - or even during, now and then - so I'm not surprised that you use both these classes of drugs at the same time. I would venture to say that for someone who already has trouble sleeping amphetamines may not be the best treatment for your troubles, but I'm not your doctor, of course... Amphetamines do work great for a lot of other things of course but maybe it's worth exploring other options.
I'm also not at all surprised that seroquel was more effective in helping your sleep than clonazepam (even though for sure the much clonazepam would make me catatonic). Seroqual is a fairly modern, targeted substance, whereas benzos on the whole are very blunt instruments for almost anything that they are prescribed to do.
Finally... maybe you just have a naturally high benzo tolerance to some extent? Mine isn't as high as yours but I've never been able to get much of anything from more than 20mg valium, sometimes 30+, even when I had no tolerance at all to speak of. Do you recall a time you used less - or has the tolerance been fairly constant - if the latter I'd say it's a good sign potentitally althogh I wouldn't be comfortable saying much more than that.
Actually - just one FINAL point - you don't necessarly need to follow the plan above - although it may be prodent to do so if you doubt your ability to plan things yourself. Diazepam obviously is know to be very low risk... but if there's another substance you like better - do some research into the duration of effects, experiment, and then maybe just stick to that one, following the same procedure. You could even try it with more than one, but obviously organisation is something you struggle with and therefore it's probably best to keep it as simple as possible, then maybe when you've moved past this, if you want to continue using in a more safe, sustainable manner, you can figure out an inviolable, concrete schedule that you must adhere to, should you br do inclined. Even that might not be the smartest idea of course, I don't know you, it's somethin, I'd probably try if I was in your predicament, once I felt more in control again, but not until after a long, extended period of complete abstinence from the class