Actually, the linguistic references and names in the country of Kalevia (Kuh-leh-vi-uh) take mostly after Finnish/Karelian. (Demyan’s the only explicitly Russian character.) Here’s a handy reference guide for Finnish pronunciation, if you’re interested.
Also, Toy-voh is a good approximation of his name. Here’s some of the others:
Kaija = Kai-yuh
Vesa = veh-suh