"Whoever is doing the forward step is in control."
???
In control in terms of not hitting something they can see and the other person can't. In control in terms of not falling over. But in control of choosing the nature and size of the movement? Unless there's a problem that contradicts it, that remains the leaders job regardles of direction.
From a purely practical standpoint, the leader can exercise more control when he is moving backwards, as in addition to signalling the magnitude of the motion, he can physically absorb some of the followers energy if she misses his intent - wheras if he's going forwards, what's he going to do, pull on her?
"To simplify things after the first three Natural Turn Waltz into whatever. Be honest, does your partner take control, or do they hold back even if the man has indicated by clearing a space for the lady to move into."
A lot of that would depend if the lowering is along a practical path. If the man drifts in a way that doesn't let the heel lower on step three, then the next step will not originate from the heel and will be weak. If the man lowers and doesn't pull out, the lady will continue crashing into the floor on the next step, etc. But if he does it right, she either takes the opportunity proportionally as he creates it, or she's decided to ingore him and dance her own version instead - hopefully because either there's someone in the way, or he's being insensitive to the fact that she's tired
"Is the right leg straight before the weight is passed onto it."
Unless she's a lot shorter and expert at using CBM to keep the hip back, I sure hope not, as I have something rather important where her leg would then be!