Katie:
Your blacks were weak because the benzo slows things down. More development time was needed.
In the dark, take a tiny sheet of that paper and place a coin on it (hold it down firmly); then turn on the room lights for ten seconds. Then, in the dark, develop the paper for the normal time. After fixation, if the paper's coin area is less than medium grey, you have paper that can successfully be used for quality prints. Proceed as follows:
You now need to know how little development you can get away with and still retain DMAX (maximum black). (Age-fogged paper is always a challenge getting sufficient black without marring the pure whites. Contrast is always the victim.) Truncating development as such will allow that coin area (part NOT exposed) be become even lighter. You now, with this experimentation, have the maximum contrast obtainable with this paper / development time combination because you have (just) retained DMAX and have lightened the unexposed areas to the best of your ability. The only thing left to do is to match your enlarger exposure to conform with this new development time.
Your final print should be somewhat darker than normal. After fixation you immerse the print in Farmer's reducer to 'bring back' the pure, white highlights. This will also help with increasing contrast a bit. (Use the combined Farmer's solution with fixer mixed in.) With this reduction you should have obtained an ideal print with this workaround. Remember, new paper is really forgiving and easy to master. With age-fogged paper you MUST zero onto the ideal development time and exposure. It's tough but doable. - David Lyga