Choosest appears a few times in the King James Bible, as does the third person form chooseth. Chooseth was also used by Shakespeare, in the Merchant of Venice, in a scene where there are several casks with labels beginning, "Who chooseth me..." Both these words will be accepted.
The past tense form chosest does not seem to be used in the King James Bible, but it is used once in another version, the Douay-Rheims Bible, as revised by Challoner. The quote is from the Book of Nehemiah: "Thou, O Lord God, art he who chosest Abram..." The King James version has "didst choose". I never thought, when I launched this puzzle, that I would need to become knowledgeable about different versions of the Bible. But perhaps I do. Up until now, I have generally taken the King James version to be the traditional translation of the Bible into English, but it seems there are other translations in general use.
From what I can make out, the Challoner Bible is to Catholics what the King James Bible is to Protestants. That is, it is the translation favoured by English-speaking Catholics who prefer a more traditional version. Amazon has numerous editions in its catalogue, so it is evidently favoured by quite a few people. To avoid any appearance of sectarian bias, I feel I should give as much weight to the text of this book as I would to the King James version.
So I will allow chosest. And what about choseth? Apparently there is such a word: "...then, with the consent of his nobles, he choseth two wives out of his kingdom; he choseth, besides, as many concubines as he pleaseth..." (Richard Chandler, Abyssinia: Mythical and Historical, 1868). [Perhaps some Ethiopian version of Silvio Berlusconi.] For consistency, I will allow choseth as well.
Theosis is listed in the Shorter Oxford, with the definition "deification". Apparently the term is used especially in Eastern Orthodox theology. I'll add this word to the list too.
