You've got three weeks which seems tough based on your scores. I wanted to score consistently in the 90s before taking the exam because based on feedback from previous test takers, the actual exam is harder and more vague than the test bank. You need to master the material such that you can reason your way to the right answer on the exam. I basically had similar test scores on the first few exams and felt I was "missing" information that wasn't covered in my bootcamp notes or my prep book, so I:
1. Read/Scan the PMBOK and took notes of anything unique in a particular knowledge / process area. (like voting, escalation procedures, etc.). BTW, these should be in the form of questions: what does a project do? so you can test yourself (testing is the most important tool in learning), just reading notes doesn't help much.
2. Cross referenced/updated those notes with material I missed from the first 3 exams (see wrong answers and answer explanations).
3. Ensure I knew major INs and OUTs, unique flows (how do deliverables flow around a project, what processes use change requests as inputs) - I printed out the PMBOK processes and made flash cards.
4. Memorize the knowledge areas, process groups. *all the test questions are really based on a foundation of what you are doing, or have just done, or about to do.
5. Took the remaining 4 tests and improved to consistent mid-high 80s). Reviewed tests and added to my notes.
6. Took the first few tests again and scored in the 90s. (it had been about 45 days since I took them last). At this point I knew I was mastering the material.
Besides testing, SPACING is as important to learning as testing. Take a test and review it the next day or the day after. Space the exams several days if not 1 week apart (if you have time) studying in-between. If June 15 is a hard-deadline it seems tough.
IF you rock the last 3 tests, you make want to retake one or two of the first tests and confirm you've mastered the material.