I should have thought that around two pounds a week was a good rate. I wouldn't worry too much about weight per se, though. So long as waist circumference keeps moving it doesn't matter if weight stays the same for some weeks.
I should carry on as you're going. Grapeseed is an unusual oil. IIRC, it's profile is OK, although a bit high in omega-6, but you want to make sure it's a cold-pressed variety you've got.