Incorrectly

Your probably not using the hammer drill correctly as well. The bounce part of a hammer drill needs to be allowed to bounce. People always try to push hammer drills into the concrete which does not allow the tool to do its job. The drill bit needs to bounce up and down as you drill. Most holes can be drilled quickly using only the weight of the hammer drill by itself while you're just hold it in place steering the bit.

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Drill in a 1/2" deeper than you need and don't worry about cleaning the dust out of the holes, who cares if dust is in the bottom of the hole as long as the bolt sets where it needs to set.

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Take whatever your using out of the holes. Go to home depot and buy appropriate sized Redhead wedge anchor bolts. Go home and tap them all the way in with a sledge hammer. Before you hit the Redhead's back the nut off the threads a bit before hitting. Position the nut so the hammer cannot hit the threads, if the threads get mangled you have a heck of a time getting the nut on or off again. Tighten the nut down with a ratchet or wrench until you cannot tighten it anymore. 2 to 3 inch anchor bolts will more than likely be enough maintain railing post integrity if someone put their entire weight on it in any direction.

Retail hardware stores don't carry industrial epoxies, I've tried multiple retail box store epoxies and they all failed in short time (excluding JB Weld... good stuff, unfortunately they don't make concrete epoxies that I'm aware of. Unless you have access to industrial grade epoxies go with the wedge bolts.

It is going to need to be replaced, its broken and you'll have to buy a new one... so use a large channel lock pliers and literally twist and break the door knob completely off. Remove all the remaining parts falling off to access the interior mech. of the door knob. Manipulate the latching mechanism to open the door with needle nose pliers.

Go to home depot or lowe's to buy a replacement.