Realistically, nothing can be done in 4 days that would raise your score by 4 points. You are going to be better of not burning yourself out, and making sure you are well rested for the exam.
UWSA or any other sort of predictor is not perfect, and 240 is likely within the ballpark of your capabilities.
For reference on some NBME for step 1, cant remember which, I got 235 2 days out, and real thing was 250
As far as 230 being a decent score, it depends on what you are trying to get into. By way of comparison I am hearing the average coming out this yr is in the ballpark of 238