In post #47 you had the follower in the correct loaction, but you were getting oscillations which I think were caused by the U3A/U4A loop with 1uF capacitor. You need a follower to prevent U5A from loading the output of U3A, but you also need to solve the oscillation issue. You'll have to do a stability analysis of the curcuit, particularly U3A and U4A to understand the source of the oscillations. I can't do that right now for you, maybe someone else has more time.