Kevin, congratulations on getting your new densitometer! Now, let me muck up your conclusions about how much film you can develop with a given developer batch. You might be surprised at how much effect the film exposure can have on this. In reality, the issue is not so much how many squared units of film were processed, but rather how much total silver was developed. The developing agent depletion and (generally) by-products released will be in proportion to silver developed. If the overall film density increases by 0.30, this is roughly double the silver being developed.

My point is that one can not legitimately specify developing capacity by units of film, alone. The best the manufacturer can do (short of recommending process control strips to monitor the processing) is to consider typical shooting conditions and then make very conservative recommendations based on that.

By the way, when you exposed your sensi wedges (under the enlarger), did you mask off the surrounding film (so that it was clear) or fully expose it (so that it was "black")? This should have a large effect on the your conclusions. The real world analogues to this might be night sky photos vs snow scenes. Just a little food for thought.