Hi Zuzya2018.
Since you were scoring in the upper 40s on practice tests it, seems likely that you are ready to score higher than you did on the real GMAT, unless you had already seen the quant questions that appear on the official practice tests before you took those tests, and therefore your quant scores on your practice tests were inflated.
So, it may make sense for you to simply take the GMAT again and make sure that you don't have to rush to the test or stress yourself out in some other way.
That said, you may want to confirm that you are truly ready for the GMAT by taking another practice test, one whose questions you are certain you have not seen, and by checking your TTP analytics to confirm that you don't have broad areas of weakness that could cause you to score lower than your goal score.
Regarding anxiety, you may get some ideas from this post.
How to Eliminate GMAT Test-Day AnxietyRegarding verbal practice questions, I'm sure there are more questions you could use, including the 1000 TTP verbal in-chapter questions and chapter test questions.
Regarding warming up, you could warm up by doing practice questions before you enter the test center so that you don't have to switch your section order to warm up for quant.
680 is already a relatively high GMAT score, and by getting just a few more questions correct, you'll score 700+. In fact, with your high verbal performance, you are positioned to score significantly higher than 700. So, stay positive and make your goal happen.