Regarding the GMATPrep test - yes, wait a week. If you waited a year, you can wait another week. There is no rush for you to take one now, you might as well simulate the test closely. Spend this week doing OG problems or brushing up on fundamentals.
Regarding the
error log - I used to keep a super detailed one until I realized I was spending more time managing that than actually studying. Basically, all I do right now is keep a tally of which OG questions I got wrong, how many times I got it wrong, and then the topic it was testing. I use that data to figure out which topics I struggle with the most, and then redo those questions + supplemental questions on the form.