I'm wondering what your recommendations would be for the best sort of product to use to inject into the pad.

@ 8oz of odorcide and 15 oz of hydrox seems like a lot of product than you're going thru quick. $$$  - Maybe switch over to Matrix Miracle, which is what I used with the water claw, not the spotter tool but a claw.  I had one recently pee the entire room put down 8 gallons of it, went to check a week later no smell at all, never used odorcide on that job.

Grant when you say that it takes weeks to dry I presume that's a Moisture reading dry and dry to the touch?

I had a cat urine job last Friday I used about 1 gallon of PetZone spiked with Odorcide. I spoke to her on Monday she said that it came out great and detected no odor. The results really depend on the extent of the contamination and know when to recommend replacement. If I need to use more that 4 in one room I recommend replacement.