Archbishop Haverland has been on Facebook, exhorting us priests to get it right with memorized texts like the doxology after a collect:
All traditional clergy should commit to memory the basic rule for expanding a collect ending to full Trinitarian form: If the prayer is addressed to the Father, it concludes ‘who liveth and reigneth with thee in the unity of the Holy Ghost, ever one God, world without end.’ If it is addressed to the Second Person of the Trinity, the ending is ‘who livest and reignest with the Father in the unity of the Holy Ghost, ever one God, world without end.’ Father is ‘-eth’, Son is ‘-est’. The two are NOT interchangeable. We don’t say, ‘You is using bad English’ or ‘He are not getting that right.’ Confusing ‘-est’ and ‘-eth’ is the same basic mistake.
There are also rules for when the Holy Ghost or Jesus Christ are mentioned in the collect: “Through the same our Lord Jesus Christ…” “… in the unity of the same Holy Ghost…”
I left a comment:
Here is an introduction to Early Modern English which includes the Renaissance period, giving a table for the declension of personal pronouns – https://en.wikipedia.org/wiki/Early_Modern_English
There will be some standard text books on English grammar of that period, and suggestions would be welcome in comments. I have a copy of Fowler’s The King’s English, which sets the standard for modern English, in much greater depth than the books we had at school, but only indirectly deals with archaic English.
Someone on the thread did make the point that we do well to have knowledge in Latin and German to understand the principles of declension of nouns and pronouns and the conjugation of verbs. The rules of English grammar have changed over the centuries, and we Anglicans (some in the Canterbury Communion and in the Continuum) use a style of English that stretched over from the mid sixteenth century to the middle of the seventeenth. I often make the comparison between our use of an archaic style of our language with the use of Church Slavonic by Russians, Ukrainians, etc. and the use of Latin by Italians. It gives a distinct otherness to liturgical language whilst remaining comprehensible to the average churchgoer.
The Blue Flower 
Some time ago, I noticed that the servers were often confused as to which pronoun to use between ‘thee’ and ‘you’: it was only when we had a conversation about this that I realized that they had never been exposed to the second person singular form ‘thee’. Now is it any wonder that they would also have great difficulty with the choice between second person singular (hast) and second person plural (hath) form of the verb used?
As I commented on Facebook to the Archbishop’s note: it is an advantage granted to those of us from the North of England, where ‘thee’ and ‘thou’ are in common use when the local vernacular is used!
I think the change in second person pronouns has been an unfortunate one. It is one of several changes in present-day English that have introduced an unnecessary degree of imprecision into speech and writing. It is one of the reasons that I insist on using the KJV Bible. I’m always running into passages where the meaning is quite different if “you” refers to several persons or if it refers to merely one. The loss of ‘thou’ and ‘thee’ has obscured some important distinctions.