Oh dear, I'm sorry you had that experience. It appears that the residue that you saw is some remaining residue from the manufacturing process that caught between the metal sheath and the tip, causing the difficulty in removal that you've seen. By the time you've received it, it will have cured and should be totally safe to clean up as you have. You've taken the right approach, with gentle pulling (make sure to pull down near the base of the tip if you're going to use pliers to avoid crimping the tube near the heating element), and once the tip is removed, give it a good cleaning with some isopropyl alcohol (or the BW-100 that you used). Everything should be working fine now, but keep an eye out for anything suspicious.