As everyone else here i have to say you have to work on your acc A LOT.
I can pass with high combos a lot of 7-8* just by spaming keyboard keys without fucking sense. That don't give me nothing. I need to know what i'm doing everysingle second in way to be usefull play a hard song for me.
The diference into AR1-2-3-4-5-6-7-8-9-10 it's the time what you have to watch the circle, use your knowledge to know how to do it, and use the song rythm/AR circle timing sometimes to do it well timed.
The way to play AR10 properly it's processing faster and better the information what you have and no by reacting faster without any control/timing.
React faster without control make you have random mieses everywhere, usually at double at slidders because you are already going out of the slidder when the next circle didn't apear. Making your plays unestable and at minimun rythm changes you fuck up.
This is easier to training at lower AR.
The way to do streams properly playing AR10 it's tapping the song bpm instead follow the rythm or read each stream circle. Only do that at streams for sure.
You can learn to read each stream circle in way to play streams with bpm changes, but there aren't a lot of these maps and usually low people it's interested on that kinda maps who change bpm everysingle combo.
I don't recommend you play AR10 until you can have high acc. Because low acc make you get lost easier and react to late, what can make you do unconsistenly jumps and hit the circles by swiming instead by know what you are doing. When you don't know exactly what you're doing you just don't improve as long as you keep trying it.
If you decide to play AR10 anyways because it's more interesting and fun for you probably you like high bpm/fast maps but you don't have the skills to enjoy high density objets (Lot of circles at same time at the screen, you can use HalfTime mode in way to enjoy that maps) : Play low AR and Easy mod, help you improve rythm acc and reading. It's all what you need to start playing AR10.
I play nomod to improve AR10 reading, and play AR10 focusing on the timing while notice if i'm hitting earlier or late make me improve my acc control at nomod and understand how reading works.
If you alternate your keys playing thats why you have bad acc. Alternate it's harder to acc than singletap because you need finger control, something what you don't need singletapping simple maps, or in the early game.
If that's your case and you use the both fingers almost the same times, you should focus on playing 2-2'9* maps where you have poor acc (D-C-B ranks), play then using HalfTime mod and retry them until you can up your acc at least a 50% more. Then move to next map and do the same. Replay that maps everyday until you can get >96% acc. Then search for new ones where you get poor acc.