4 ideas
When Chava marries the Christian Fyedka and converts, he sits shiva for her as if she were dead. Each concession to love-marriage stretches his tradition until one crosses the line where bending would mean the tradition no longer exists.
Tevye constantly cites scripture and liturgy slightly wrong or out of context, bending sacred verses to comment on milk prices, horses, and heartbreak. The garbled quotation lets him complain to and about God while staying inside the language of piety, so faith and protest share one sentence. Reading his errors as deliberate or half-deliberate shows how a devout person can voice doubt without leaving belief.
Tevye tells one loss after another in a chatty, digressive, joking voice to a listener: a daughter's drowning, his wife Golde's death, and finally expulsion from Boyberik. Humor puts distance between the speaker and the pain, so he can keep narrating without being silenced by grief. The laughter also dignifies the teller, making him the author of his misfortune rather than only its victim.
Tevye becomes a dairyman after a chance act of kindness toward rich Yehupetz families brings him a cash reward. He is then undone again by a relative's failed speculation and by imperial decree. His economic life depends on luck and on the goodwill of wealthier outsiders, never on accumulated security, so every gain can be reversed by forces he cannot control.