For grammar generally yes, regarding the vocabulary though there are some words which have origin clearly neither Italian nor Istro-Romanian. Mižul is one example, jezera is another (means “thousand”) etc. there’s many more of them.

Oddly enough there are a lot of Germanisms too, ex. you’ll say luft instead of zrak.

Ah, we use glaž too. Some also say maštaleta, but it depends from place to place. Two adjacent vilages in Istra will often have completely different terms denoting the same.

Never heard about kupica.