Laura's infirmity cripples Tom, stuck with the double responsibility of being the family breadwinner and 'supplying' (from the warehouse!) a suitable mate for his handicapped sister. Plus he has to put up with Amanda's eternal prattling about the glories of her youth and fuss over Laura's uncertain future. He is the 'chief cook and bottle washer,' a one-man-band, and finally cracks under pressure. Who wouldn't?
Tom confides to Jim early on that he has used money destined for the electric bill to pay Marine Merchant dues. Be it theft or treason, this clearly shows Tom's need and priority 'to get out' of a no-win situation and to find a life of his own.
Tom indeed follows in his father's footsteps by breaking away. Does he send money back home to still support his mother and sister? He does not say, but this would seem the most "suitable way" to meet his family's needs as well as his own.
Couldn't he have found another job or, as Jim, bettered himself by taking night courses? More than money or education, Tom needs vital space; for at home Amanda, though endearing, eats up all his air. As he takes the fire escape for the last time, his flight is physical but his "escape" is first and foremost a psychological one.
From Laura's standpoint, when she dances with Jim, though haltingly, something else other than the unicorn breaks - her inhibition and lack of self-esteem. She finds resources within herself 'to move on,' even without Jim.
I would suggest that the paralysis in the play is definitely broken with the desertion of Tom. After Tom leaves, Amanda and Laura will have to break free from the strict conformity that has defined their lives up to now. Tom, the only breadwinner, is gone. I'm sure if Williams wrote it, Amanda would reflect that her son was just like his father, a man who fell in love with long distance.
Inevitably, Laura will change, she is already changed from her experience with Jim. Why else would Laura feel so elated when the unicorn is broken and changed into a regular horse. There appears to be a psychological change in Laura. She has, like the horse, lost that which makes her different. She has had a romantic moment with Jim, even though it does not work out, it changes her forever.
"LAURA: Haven’t you noticed the single horn on his forehead?
JIM: A unicorn, huh? —aren’t they extinct in the modern world?
LAURA: I know!
JIM: Poor little fellow, he must feel sort of lonesome.
JIM: Aw, aw, aw. Is it broken?
LAURA: Now it is just like all the other horses.
JIM: It’s lost its—
LAURA: Horn! It doesn’t matter. . . . [smiling] I’ll just imagine he had an operation. The horn was removed to make him feel less—freakish!" (pg. 86-87, Williams)
An interesting question. Within the play, I'd have to say no, no suitable way of breaking free is shown. All the actions taken—denial of reality, working, retreat into nostalgia, trying to get Laura a boyfriend, etc.—either reinforce the paralysis, cause it in the first place, or fail to really create an escape. Tom's final speech describes a physical leave taking, but he's still clearly anchored in that apartment, as his final paragraph starting "Oh Laura" indicates.
Now, if we might speculate about what might allow them to break free, it would be, to be realistic, small steps and reworking the entire family dynamic. Amanda would need to get out. Laura would need to do something, anything different—a short term class, baby sitting, anything to break this glass menagerie.