Here are the instructions right from the distributor:
https://pim.integratedmedsys.com/Brands/ICU/Smiths%20Medical/PDF/1641407209_AcapellaPatientGuideBrochure.pdf
I'm not sure why yours melted - perhaps it came into contact with the bottom of the pot? I use a round silicone mat (hot pad) in the bottom of my pan, set the heat to just keep it boiling, and have not had such a problem.
But, you can use (fresh) 3% hydrogen peroxide for 30 minutes, or 70% alcohol for 5 minutes to sterilize as well.
My friend, a retired health inspector, says the sanitizer used for beer bottles, bar glassware, etc is not adequate for TB, so I think it is not OK for NTM either.
Sue