In general, most people would agree that if there is no improvement after a second attempt at a course, a third attempt or beyond is very unlikely going to make any difference.
If you get at least a C (not including C-), I think the general rule is to just leave it and move on. You passed the course, and it is not worth your time repeating it. You can show improvement by doing better in a subsequent course (i.e., Ochem 2). Had you asked about this after your first attempt, I'm sure the consensus would have been to not even bother with the second attempt.
When AADSAS calculates your GPA, all attempts at a repeated course are factored in, regardless of how your institution handles such situations. They recalculate everybody's GPA rather than just take that provided by your institution so that the playing field is more even for all applicants.