As the singular, with you/ye as the plural. (Then later you was used as the formal form with thou as the familiar, like French's tu vs vous, and then later the informal thou/thee fell out of the use. [And new plural forms were innovated, e.g. youse, y'all etc.])

Right; classically the counterpart to "you" in English would have been "usted" in Spanish. (Not really anymore, of course, since English doesn't use the formal/familiar distinction.)

Correct. In German its "du" if I remember right.