It's ok to sing into the mic, or hell, scream into it, it's what it's for. Just don't blow on it to clean off dust, etc. Always use the wind screen outdoors, in case of gusts, and just to reduce wind noise. And I'll tell you, send the defective zipper pouch back to PMI Audio, and I'll bet they'll just replace it. A pop filter is a good thing, and in my experience, a wind screen can dull the highs on a vocal mic. You notice we use foam to block high frequency noise in studios, right? Why would you wrap your mic in it unless you have to? Go to a sewing store and buy a 6" embroidery hoop, maybe $5. Stretch 2 layers of panty hose over the inner ring, slide the outer ring over it and tighten it down. You can use some coat hanger and a mic clip or an office paper clamp to fix it to the mic stand. This is needed only for vocals as a rule, but can also be used for wind instruments such as flute.
Good singers who use proximity effect as a tool will want the pop filter as close to the mic as it can get without touching it. You may however, place it further from the mic, say 6"-8", to keep less experienced singers a minimum distance from the mic. Put one of those silica gel packets in the bag with the mic to keep it dry. High humidity or rapid changes in humidity can cause condensation that will make the mic crackle. You can dry it out and it will be OK, but it takes time.-Richie