I have made a livey style forge this month also, one thing I altered was the blower system, I made the mine with the straight pipe also, but instead of capping the end off, I made a swivel plate on the end. The reason for this was that I use a 20 dollar vacuum (wet/dry vac cap for 5 gallon buckets) on exhust to push the air into the pipe. the plate acts as a governor on the air flow, The more I block the end of the pipe the high the air pressure exiting into the forge. Biggest draw back so far is the noise of a small vac while heating metal, but the process works great.
As for the adobe mix I used potter's clay from a craft store, sand, and a couple of handfuls of wood ash to make it. Equal parts sand/clay, just enough water to make it mix together, and the two handfuls of ash. takes a good 5 days to a week to dry enough to put any fire into it. And while the adobe is a great insulator, you'll prolly want a bench or stand to mount the forge on so you're not bending over all day while working. great examples in the pics above.