Disappointing Score Result (660) and When to Call it Quits

Thank you for your input. I think largely much of my frustration seems to come from how little progress I seem to have made despite hundreds of hours of study. In regards specifically to your questions:

1) I took an in-person GMAT prep course of my city of residence last fall, which while helpful was not in depth enough for me to progress to my goal scores. I sat for the GMAT once in February and it was frankly a disaster - I felt woefully unprepared and was sick with a bad cold the entire week leading up to it and immediately cancelled my score following that exam (I think it was around 600ish). After a week to get healthy and reset, I then switched to Target Test Prep full time in late February. I basically completely neglected verbal until mid-May, I'm naturally pretty good with SC and RC but my weakness is CR. These mocks were all official mocks and taken legitimately.

2) 5/16 - 660 (44Q, 36V) zero study for verbal at this point
6/5 - 650 (46Q, 34V) had some big time time management issues on Verbal here
6/12 - 680 (41Q, 41V) finally the verbal breakthrough I was looking for, but tried the whiteboard thing for Q and suffered significantly with time management
6/26 - 670 (44Q, 38V) taken about 5 days before my exam
GMAT ONLINE: 660 (44Q, 36V)

I realize my score deviation here indicates I would get basically exactly what I got, I suppose I'm more at a loss why there is seemingly no improvement despite continued hard study. I rarely get verbal problems wrong in practice and was surprised with only a 36V after finally feeling like I broke through to the 40 range. I would've been satisfied with a 680-690 and felt like on a good day I'd get that, but rather seemed to perform on the low end of my abilities.

3) Looking mostly at schools in the 20-30s range such as Vanderbilt, Emory, UNC, CMU, PSU.