Have you read the King James Bible,? "Thees" and "Thous" are 2nd person informal while "you" is actually the 2nd person plural/formal. In the Vulgate of St. Jerome you see the 2nd person informal. For example in Ezekiel 28:12

"et dices ei: Hæc dicit Dominus Deus: "Tu signaculum similitudinis, plenus sapientia, et perfectus decore." (vulgate)

"And say to him: thus says the lord god: you were the seal of perfection, Full of wisdom and perfect in beauty" (New King James)

If you look at the original Greek of the new testament you see the same use.

1st Corinthians 1:6 "6 καθὼς τὸ μαρτύριον τοῦ Χριστοῦ ἐβεβαιώθη ἐν ὑμῖν, 7 ὥστε ὑμᾶς μὴ ὑστερεῖσθαι ἐν μηδενὶ χαρίσματι, ἀπεκδεχομένους τὴν ἀποκάλυψιν τοῦ Κυρίου ἡμῶν Ἰησοῦ Χριστοῦ· 8 ὃς καὶ βεβαιώσει ὑμᾶς ἕως τέλους ἀνεγκλήτους ἐν τῇ ἡμέρᾳ τοῦ Κυρίου ἡμῶν Ἰησοῦ Χριστοῦ."

ῡ̔μᾶς • (hūmâs) Attic accusative of ῡ̔μεῖς (hūmeîs) ῡ̔μεῖς • (hūmeîs) second person plural personal pronoun: you (ye, y'all, you guys)

I have not looked at the Hebrew but it is unlikely that the Early Christians would have used a different address for God. This informal address is how 1st Century Jews and Christians would address God. However, there probably would also be a lot of adjectives added (Lord my God, King of Kings etc...) depending on the person and situation.

http://www.sacred-texts.com/bib/vul/eze028.htm#003 https://sites.google.com/site/nestle1904/1corinthians https://en.wiktionary.org/wiki/%E1%BD%91%CE%BC%CE%B5%E1%BF%96%CF%82#Ancient_Greek

The split commonly found in Indo-European languages between informal (usually only grammatical singular) and formal (usually only grammatically plural) second person pronouns is a relatively recent development--per Brown and Gilman (1960), this politeness distinction (tu as informal, vos as formal, T-V for short) shows up only in the fourth century, with vos used to address Roman emperors, and not consolidated into the forms we see today for several centuries. There's some reason to believe that this politeness dynamic existed before we see it in the written record, but it's also quite clear that until then the primary axis distinguishing T and V pronouns was number: tu was used exclusively to address a single person, while vos was used for groups. There are a few competing (though not necessarily exclusive) theories about the development of vos from a simple plural to a respectful singular, but Brown and Gilman focus on the two seats of the Roman Empire, and the nature of the emperor's person, as two key reasons for the shift:

Words addressed to one man were, by implication, addressed to both. The choice of vos as a form of address may have been in response to this implicit plurality. An Emperor is also plural in another sense; he is the summation of his people and can speak as their representative.

This reanalysis of a difference in number as a difference in politeness spread to different places at different times: per Popov (1985), we first see East Slavic/Russian vy used in the singular only in the 15th century, about a millennium after the first attestations in Latin. He dates analogous phenomena in German courtly language to the 9th century (first with Ihr in the 9th or 10th century, then Sie from the later 17th), in French to the 12th, and in English to the 13th. Brown and Gilman don't spend much time on the precise chronology of the developments in more vernacular registers, but in French, Italian, and English literature these politeness dynamics established themselves in some form by the 13th, 15th, and 16th centuries respectively.

All of this is to say, people speaking Indo-European languages started addressing God with a T pronoun basically from the time of conversion, because it was the main form of address for a single person. The development of polite V pronouns post-dates Christianity by some time. The widespread consolidation of V pronouns as formal terms of address dates even later, since this change had to spread not just from court to court, but out from courts to the wider population. It also didn't take hold everywhere: as Popov notes, modern Russian speakers from less educated backgrounds often dispense with the politeness distinction altogether and use ty indiscriminately for individuals, whatever their relative social status or personal dynamics.