When Dennis was summarizing Vaclav's mistakes, he referred to the step-son but called him Vaclav's son-in-law.
At 47:25, a stage light is visible in the upper right corner of the screen.
"Maryska" or "Mariska" is an eastern European diminutive, meaning "little Mary". (Hence e.g. Mariska Hargitay whose father was Hungarian.) It doesn't work as a family name.