The pronoun "wasz" means, that the, so-to-say 'owner' is multiple (some children) and the object is singular (their dad).
They are 8 types of pronouns in Polish (see a quite complete list in Polish here or another a bit less complete list in English here). "Wasz" falls into 2-nd category - zaimki dierżawcze (possessive pronouns). and they reveal:
- the number of owners (singular / plural)
- the gender of owner - only in 3-rd person singular
- the number of objects (singular / plural) - except for 3-rd person singular/plural
- the gender of object (singular male, singular female, singular neutral, plural male, pluram female or neutral) - except for 3-rd person singular/plural
See a table below:
Yes - plural would be wasi - masc. personal or wasze - non-masc. personal
Singular as for 'dad' - because there is one dad. Your in this sentence is plural you. With singular you it would be ' twój tata'.
Duo offers two meanings for wysoki - tall and high, but in this sentence it only allowed "tall" and "high" marked as incorrect.
Yup. I'm pretty sure that "Your dad is high" would mean that your dad is on drugs. Not what the Polish sentence says.