In naẓartu ḥiwārahu, the verb conveys watching or waiting. Ḥiwār often means conversation or reply, but here the relevant sense is awaiting the result or response of the drawn gaming shaft.
ʿAlā al-nār belongs to the scene of treating the object with fire. Reading the entire line as a normal conversation between people, or treating the qadaḥ as a wine goblet, would obscure the adjacent commentary and historical setting.