The nomenclature used by repair techs is the key you press to play F is the "F key". The next key you add to play E is the "E key", and the last key that you add to play D is the "D" key. The somewhat smaller key directly above the F key is called the "F# key" since that is the key that closes when you press the E key alone to play F#. I hope that makes sense.
When regulated properly closing the F key or the E key alone (to play F#) should completely close the F# key at the same time. Some techs adjust the D key to also close the F# key, and some like myself leave it a bit light. On some vintage saxes the "back bar" of the F# stops after the E key and so the D closing the F# is not an issue.
Typically to regulate this area on the bari sax a tech will bend the back bar of the F# up slightly and seat the F#, F, E, and D keys independently of one another. Then the back bar is bent back down to where it was and the F, E, and D? key feet are bent up or down to independently close the F# key at the same time. Usually the low Eb or C key is removed and a leak light is inserted into the sax to make these adjustments.
If you can rig up some sort of leak light and are comfortable removing one of these lower keys, and can give me a clear description using the nomenclature above, I can talk you through a "quick and dirty" method to adjust the regulation on your own. It probably won't be perfect, but will be better than it was.