I mean, don't get me wrong, everyone makes mistakes, but you quitting cannot be a financial decision right? To make 120k, you need 15k day*rates to go. At 75$ for your rate, that's 200 days. With ~260 actual available days to work, you expect 77% efficiency? With the taxes, insurance and most importantly, the presumed availability of work .. There is no way.

I have been doing consulting for a while and as an advice, I would take the efficiency to be at most 50% so in OP's case would not accept less than $115/hour to quit my $120k job.