To John Phillips -- You can remove the broken portion of the screw
from the wooden rail with a *screw extractor*, which is simply a drill
bit with a reversed thread, available at your local hardware store.
They come in different sizes; select one slightly smaller than the
shank of the broken screw.  It will help to heat the screw before
doing this.

With the screw extractor in an electric or manual drill, drill into
the shank of the broken screw in clockwise direction, until the
extractor is solidly anchored in the shank (about 1/4" or 2.5 mm
should be enough).  Remove the drill, leaving the extractor in the
screw shank.  Using a wrench or pliers, grasp the top of the screw
extractor and turn it in a reverse (counterclockwise)direction, and
it will draw the screw shank out of the threaded hole.

There are other techniques for removing broken screws; see Art
Reblitz' "Piano Servicing, Tuning and Rebuilding", page 84.

Re your treble hammers that have come unglued; from the piano supply
houses you can buy a set of the top 10 or 20 hammers to replace these.
You could re-glue the old ones, but they will probably not sound too
good because the tension of the felt has been lost and cannot be
restored.

Larry Lobel