I've not come across R22 and ammonia reacting, would be interested to know more about what you found. As for the sludge, can you find out what it was? Blue/green does sound like copper if it's a vivid colour, but aluminium salts are often pale blue-green. As for checking the amount of R22 still present, if you can find a lab that can do ammonia analysis they should be able to do something for you. It's not something that would normally be analysed for, but if they have a method that looks for air gases then they might be able to modify it to look for R22.