Why isn't this in the intrumental case? Shouldn't it be "To jest domem," or is that just for animate nouns?
The construction "To jest/są" is an exception. Nominative is used as a complement of the identifying phrase to jest/są - that is/those are: To jest nowe muzeum. That is a new museum-Nom. To są moje okulary. Those are my eyeglasses-Nom.
"Ten jest dom." doesn't work? Or is "ten" "that"?
„Ten dom” or „To jest dom”. In Polish: this House/Child/Girl - „ten dom, to dziecko, ta dziewczyna”, but: This is House/Child/Girl - „To (jest) dom/dziecko/dziewczyna”