Consider giving the 3star range a bit more practice before you try to go past that. You've got some nice scores, but a lot of low As on 4star maps (which you generally want to avoid going for).
Personally I'd recommend collecting more S-ranks on 3.5-4 stars for a bit, that should help you transition into the higher intensity of 4star charts more easily than just trying to mash them out. Longer charts are also better if stamina is your concern. Stamina comes with time, especially when you're trying to make yourself go faster.
You seem relatively fluent in the 2.5-3.5star range, but don't be afraid to work on those scores too, you'll have a lot easier of a time securing a variety of higher-speed S-ranks if you've mastered all the slower stuff.
EDIT: I see you play a bit of 7key. I do not play that mode, so take anything i tell you with a big grain of salt.