Well, thanks, Ryan for the new word for me: illeism - ( )
The practice of referring to oneself as "he" or "she", or by one's name .

I've heard small children executing this illeism, most notably a little five-year-old boy who was instructed to sit down along with the other children, and he said,

"Jeremy don't want to.

Of course, to make his use of illeism a bit more grammatical (under the circumstances), he should have said,

"Jeremy doesn't want to..



Back to your question about "I." "I" is simply a first case singular pronoun, and it takes the first case singular verb "am" in order to have subject-verb agreement. "I" functions as the subject of the sentence and "am" as the verb.

Does this answer part of what you're asking?

I would say your "illeist" example of "Ryan's" taking a first case singular verb is simply ungrammatical. In order to be grammatical, the word "Ryan" requires the third case singular verb. "Ryan is going to the store" is a grammatical sentence, but becomes illeist only if you, Ryan, speak it.

Hope this helps a little!

BEst regards,
WW