7k will not benefit you in 4k in any significant way.
honestly just play more maps, at this star range there isnt that much to improving other than playing more and familiarizing your muscles with faster things.
also, yes, etterna is a pretty good game to play if you're going for improvement. it wont magically boost you up into being able to play everything but its a good place to start on. its difficulty calculator is a lot more accurate and can distinguish different skillsets and patterns. if you would like help setting up etterna shoot me a dm