I'm a little confused by what exactly your program is. Pin presses are not in the NLP. If your BP and PR are getting stuck there are a number of things to look at first (The First Three Questions | Mark Rippetoe) and if all is ok, then a shift to advanced novice programming is generally most useful (this will also generally not include pin presses).
Putting the above aside for the moment, if you don't have BW chin-ups, you will likely need to give them dedicated focus with some more "slots" than are in the standard novice program (especially given your age). I'm not a big fan of negatives for this goal and if you have other options, I would use them. I would try and have at least 2 sessions each week that work to build your chins getting in around 25 total reps between assisted chins and lat pull downs.