What are three incidents that caused significant change in Tom throughout The Glass Menagerie?

There are specific moments that help to serve as catalysts
for Tom's changes in the play.  Yet, there is a general current that causes him to
change, in general.  For example, the reality of Tom's father having left the family is
something looming in Tom's psyche.  He cannot shake the reality that his father left. 
It is not that Tom seeks to be the same or different as his father, but his father's
actions are omnipresent in Tom's frame of reference.  In the end, this helps to cause
Tom to see abandonment as a course of action to be taken.  The constant bickering with
Amanda helps to drive him away.  Tom is seeking a life that is one where definition is
not clear.  This fluidity is not helped with the dominating and intensity of Amanda. 
The moment where Tom does not use the money to pay the electricity bill might also be an
instant where Tom demonstrates his change.  In not paying for the lights, Tom makes a
definite statement that his loyalty might lie elsewhere and is a moment from which there
is no turning back.  Tom's thoughts and surmising about leaving are brought into reality
with an absolute action that demarcated a line that had been
crossed.