You fell for the advertising BS about chemical drain cleaners. They don't work and, as you have described, they create a hazard for the plumber you will still have to call. Your drain needs a profession with profession equipment to clear the clog. Plunging won't clear a drain clog, only a clogged toilet. Don't jump to quick conclusions about replacing your drain. Get on the phone and get a plumber ASAP, but avoid companies with "Rooter" or "Roto" in their name.