Jumping from a R3 to a ZX10R isn't just about your right hand's temper. You got to also realize on mistakes as well. An accidental over blip of the throttle on the R3 leads usually to nothing while on the ZX10 will probably lead to a crash. In other words, don't make any mistakes.
Also all the things you will sacrifice. Like livibility and comfort and ease of handling. All that is going out the window. You will actually have to control that bike. You will sometimes just fight with it to try to be its master instead of it controlling you. You will most likely have considerably less comfort or pain or fatigue. You will be a mess of nerves for a good time, if not forever. Slow speed handling will be worse. Far worse. The R3 is bad compared to a naked upright. Add another 60 pounds and an aggressive posture with all the weight in your hands, and the bad slow speed handling is amplified. I really hope you won't be doing any stop and go with that thing. And the last thing I hope, I hope you won't live in fear with that machine. Skill levels are all over the place. Some people will handle it fine. But then, I know some people who just lived in fear for years owning similar machines. As in, even 3+ years with it, they ride afraid of what is between their legs. Personally I don't understand why some people even do that. Hopefully you will not be one of those guys.
I would advise you to see if you can get a test ride on that thing. You should be able to test ride used motorcycles.
I fully understand how it feels starting from a 300cc, wanting something stronger. But in a few years from now after you got the 1000cc super out of your system, and if you ever are able to get back on the 300-400cc, you'll appreciate it in in ways you've never before.