When you do alternating renegade rows, try pushing the non-rowing hand into the floor. That will help stabilize you. So, as you are pulling with one hand, push with the other. Same thing if you were doing the "Plank row" all on one side first. You should always push the non-pulling hand into the bell/ground..
I have to ask..You are using a 8kg for the row..What size is the other bell? I really can't recommend Renegade rows on anything smaller than a 16kg bell, and that's pushing it for a guy your size.