You should scuff up the outside of the rind first, so there are avenues for the oils to escape. Smaller chunks as well.

Also, use a pressure pot on low heat. Too much heat will destroy certain suspended acid crystals, breaking them down and reducing their potency. Try your best to avoid taking it to a rolling boil.

Watch this for a better idea of how to extract the full essence of a tropical fruit:

https://www.youtube.com/watch?v=hZT6r1CC6hs

I don't expect you to get all that equipment...

But the concepts he describes are sound, and will help you understand exactly what component of the fruit has the active ingredients for a remedy.

What you're doing will still work. But your yield can only improved considering your current set-up.