A long stemmed, and narrow, flat-blade screwdriver, inserted below the underside of the ink cart, got me out of this exact bind once. To see the motion you'll need with the screwdriver, eject one of the "working" ink cartridges to examine the cart retention mechanism. It is, essentially speaking, a pry-downward-to-release sort of motion, such that the retainer pin disengages with the cart's underside. After the cart is out, bend the retainer arm upward so this doesn't happen again. If my experience serves as a template, you'll be fine.
The ink volume in your cart has no impact, in my opinion.
John Caldwell