What is the function of the small twist nob that tightens or untightens - located half way down the length of the pendulum, but attached to the inside wood clock body. Also, is there a way to eliminate the clock chime @ the half-hour and on the hour?

To adjust the loudness of the chime.

See
Instructions for operating 31 day wall clocks (http://www.clockmd.com/manuals/31daywall.htm)

It appears you can bend the hammer to eliminate the chime.