Wait!! MD83FO!
Just read what you wrote about calculating a descent path to cross the threshold at 50 feet?!!!! Ehhh, do you not disengage the auto pilot at minimums or before that if visual, disengage flight director and engage TRK FPA and ask for RWY TRK to be set and fly visually.
On the JEPP charts you have the distance vs height layout to tell you exactly wether you are above of below the profile. Why try and make it astronaut business when it's not?!