Yea, given your ADHD, it seems that focus is your biggest concern. Focusing, relaxing, and confidence for me were the difference between a 4-5 and a 9-10. I did all three of those things by removing all thoughts from my head and staring at the passage. On the real exam, I found my focused state by sitting completely still with my left hand on my beard and my face stuck facing the screen. The only things moving? my eyes and the tips of my right hand's fingers. Everything else stayed completely still for 45 minutes. Near the end of the section, I couldn't even feel the pinky on my left hand and both my legs were asleep. Was it worth it? absolutely! I was completely focused on that test and thus I understood the passage soooo much better and most of the questions could be answered by common sense as a result
As far as time goes, I would suggest not focusing on it so much (I know, it sounds really hard, and it is). By this, I mean dont stay strict to the 8 minute rule for each passage. Focusing on time causes urgency and anxiety and as a result, you lose focus on the passage. Focus on the passage should be your #1 concern. Dont ignore time, but dont emphasize it either. You should read the passage as fast as you can while also trying to completely understand it. On the questions TRUST YOURSELF AND GO WITH YOUR GUT! every once in a while, glance at the timer just to make sure you haven't spent too much time on the passage. I think you can be flexible with your time a bit by going 10 minutes on the harder ones, but making sure you go faster on the easier ones to make up for it. I use to check my time on the 4th passage by seeing how many minutes I had before the half way mark to see if I had to speed up or I could take my time a little bit. When I first started studying for the section, I was at 28 minutes left when starting the 4th passage, and I wouldnt even finish the section. If you still have over 35 minutes remaining when you get to the 4th passage, I think you're fine.
Perhaps you already know all this and you're already scoring 10s, but want to go higher. If so, sorry for wasting your time lol. What range are you scoring in?