No, "to" is a part of the phrase "je to/to je" ("jsou to/to jsou" for plural), which was used in the sentence above (in plural). It is used to identify people/things/etc.
If you stripped the sentence completely, you could say "Jsou to osoby./To jsou osoby." like you'd say "Jsou to muži. To jsou muži. Jsou to ženy. To jsou ženy." The "to" does not change with gender, you only adjust the verb to match in singular/plural. For singular, you'd say "To je muž. To je žena. To je osoba. To je jiná osoba." If you wanted to specify "the different people", you'd say "To jsou ty jiné osoby./Jsou to ty jiné osoby."
I'm afraid not. The Italian "C'è" matches with the English "there is/are" or the French "il y a" or (more or less) the German "es gibt". It does not have a match in Slavic languages.
This "to je/jsou" corresponds with the German "das ist/sind" or the French "c'est/ce sont". In Italian I would simply use È/Sono. In this case: Jsou to jiné osoby=Sono altre/differente persone.
You're right. The last sentence (nejsem to žena) is incorrect. However, in your sentences, you're not using the phrase that I was talking about, the "to" has nothing to do there.
As you might have noticed the phrase "je to/jsou to" uses the verb conjugation for 3rd person (either singular "je" or plural "jsou"), but your sentences use verb conjugations for 1st and 2nd person. To help you identify the phrase, you could ask a question "What is it? (or equal question in plural)". Then the answer to this question would contain the phrase "je to/jsou to". "What is it? Co je to? - It is a dog. To je pes./They are dogs. To jsou psi."
Remember to distinguish between 'to' as an adjective and 'to' as a pronoun. As a demonstrative adjective, 'to' can indeed mean 'the' or 'that'. But as a pronoun, as here, it means 'it' or 'they'.
As a pronoun, 'to' can be used with either a singular or a plural complement, so it can mean either English 'it (is)' or 'they (are)'. The Czech verb will tell you whether singular or plural is being used.