Just how detrimental is a 1480 (790M, 690 CR) for Harvard? Is it worth it to retake and try to raise my CR score by 30 points?
Your 690 CR&W score on the new SAT concords to a about 650-660 on each of the two related sections of the old SAT. According to the CDS from 2014-15 for Harvard 78.47% of the freshman class had a score of 700 or greater on the old SAT CR and 80.17% had a score of 700 or greater on the writing section.
Retaking the SAT might help, but you should be sure to focus on everything you need to do for the rest of the schools on your list.
If you’re really interested in Harvard, I would indeed try to raise your CR past that 700 benchmark.