Forget GC and take job first.

If I were you, I will definitely take the job first and just resubmit a new petition by new employer for the Green Card. The green card is the one that anybody can get but obviously the chance for job is not. My understanding is if you move before you get I-140 approved, you will no doubt give up the current GC petition by your current employer. But If you get I-140 approved, you maybe have a chance to keep your current EB1b application valid but you have to work 6 months or more after you filed your I-485.