Thanks GMAT club for all your advice and the
GMAT club tests (I worked about 8 of them). It took me two attempts, but I went from a 640 on my first attempt to a 720 (Q47/V42) today! I shall never take that exam again in my lifetime. I knew I had a 700+ in me, but it wasn't coming through. On this final attempt, I believe I had a few more skills, a lot more practice and a little better test taking strategy, which was the result of more practice. For anyone out there struggling with the GMAT, I can not stress the benefits of practice working problems enough - quant & verbal, particularly OG problems. I worked the quant problems in OG12 probably 4 or 5 times, and learned something new each time. There are consistent patterns to GMAT problems. Learn them. Knowing the patterns will help you answer questions correctly even when you don't know the answer.
God Speed!