Leaking through the bottom and losing product or past the stopper and leaking to the bottom of the tube? Assuming the former since you said it doesn't pump.
I would remove the top. I've done it before. Bottom might work better. Not sure. Then just use an oral syringe to measure out a dose. I'm not sure how many ml in a pump atm. Maybe @delsolrob can answer this. I'll look into it though.
Can't say I've ever encountered this problem myself, but anything I'd possible. . I do remember when BPS was producing it, I had issues with inconsistent pump sizes. I actually recently threw out a BPS bottle that was about five years old. The gel had turned to liquid and again pumps were very inconsistent.
