All good advice given in the previous posts... I too, think you had a combination of both too much smoke and probably too much heat. Get that digital - I highly suggest the Maverick ET-73 dual probe, as you can measure both chamber temps and meat temps (don't need internal temps for ribs, but many other meats you will).
Place a chimney of unlit lump in your firebox. Add a chimney of lit lump to that, along with a few chunks of your favorite wood. As was said earlier, open the chimney all the way! Get the unit up to temp and wait a bit for the smoke to settle down, place your meats on the grates and adjust the temp with only the firebox vent.