That was me as well. A lot of people told me to do uworld and forget First aid. But take that with a grain of salt. YOU know what your true weaknesses are. It sounds like you had the same issue as me, it came down to just a cold hard fact. So what I did In a day was 60% UW and it’s explanations and 40% of content review in FA. I can truly say during the exam I was getting the stuff I was missing only because I did review my weaknesses on FA, cold. So with 3 weeks left, try dividing your day like that.
Also when did you take these NBMEs? I’m not a big fan of NBMEs. They’ve always been lower than my UWSAs. But I’d say if you can try doing NBME 17 (got a couple questions verbatim from there), NBME 18, and Free 120.. That would be solid. My exam and a lot of other people’s exam felt like UW and free 120. I don’t know if it’s possible but the new NBMEs are highly recommended too. I just didn’t have the time to take them.
I think if your UWSA2 comes back as 240+, your next NBMEs are around 230+, and Free 120 is 80%+, you are in a good spot to set yourself up for a 240 if exam day goes well for you.