The questions were completely missed because of the very long story.
To be perfectly honest, sonice you are asking where you "stand legally"
in this situation, you should consult counsel. I take it there is a
considerable amount of money involved and that you are considering some
sort of action. I am concerned about this statement "They did not put
in writing what was to be done". You may have limited your options by
not insisting a complete description of the work be in writing. Again,
seek legal counsel.