Some of those unfinished books are probably not necessary. I think that you will be fine with the eight Manhattan guides, the OG, and
GMATClub Tests.
You can also complete the six Manhattan online tests, but the
GMATClub Tests are better for quant. You can also reinstall the GMATPrep software, but since you practiced with two tests already, view any additional tests as a confidence booster rather than a reliable score estimator. They might inflate your actual performance.
And take the test whenever you're ready. If you truly need another two or three weeks, then reschedule. The GMAT requires hard work and consistency. If you feel that something is lacking in your preparation, then do whatever is necessary to correct this problem.