Honestly, in my opinion, if someone takes the IELTS test after good amount of practice knowing the exam pattern well, the score they get is more or less the final score for their level of English. Any attempts with more practice could push scores up only by 0.5 or so. More than that would be extremely hard. I feel the test is very matured and standardized, and reflects the standard of a person's English with reasonable accuracy. It is evident from your case and I felt the same when I took the practice and real tests. Scores didn't deviate much for me from Cambridge practice tests to real tests.
Are you not interested in other PNPs?