A lot of problems here.
1. εἰμί (a form of "to be") is in the 1st person singular present tense indicative mood. This means it should be translated as "am". "I have" or "I have been" would be in the 1st person singular perfect tense indicative mood, which it is not.
2. Strangely he has it as "I have seen" even though the word "to see" ὁράω or βλέπω doesn't show up at all in the text.
3. This person is going off of a simple concordances even though concordances like the NASB don't always have definitions corresponding to the literal meaning of the verb, rather these concordances give a range of how it could be read in English to make it easier to understand rather than what the verb really means.
4. He uses the Modern Greek είμαι. Now I don't know much about Modern Greek since I only took Koine and some Attic, but basically what this person is doing here is called the etymological fallacy. Just because a word used to mean something doesn't mean it has that same meaning now, or just because a word has a meaning now doesn't mean it always had that same meaning. I will say this though, the Modern Greek eimai generally does mean "am" the same as eimi in Koine, again his use of concordances is fallacious for finding the true meanings of these words.
5. He uses John 3:28 where many translators do translate this as "have". Well, many translators also translate this as "am"
What he fails to realize here is that in the versions he quotes these are simply the translators translating it in the perfect tense in order for it to flow better in English rather than translating literally. It's simply their choice. This happens all the time when translating the NT, sometimes you can't translate so literally or else it will sound awkward in English. Why do you think we learn Greek in the first place? Because even though many times translations can express the meaning well, they can never express it like the original language. Take for example John 14:9 where Jesus says to Philip, "Have I been with you so long, and you still do not know me?" Literally "eimi" is used here, but many translators choose to use the perfect tense instead because it would sound slightly awkward to use "Am I" like "Am I with you so long a time, and you still do not know me?" (Although some translations do have it that way like BLB).
In fact, non literal translating is done right here in John 8:58 with the verb γενέσθαι which means "to become" since it's infinitive, yet many translators choose to make it imperfect because it would sound weird translating it as "Before Abraham become, I AM."
6. This is where I think his argument really falls apart. That is, John 8:58 is well situated in the numerous "I am" sayings in John which simply cannot be translated as "I have" or "I have been".
John 10:9, "I am the door/gate", literally ἐγώ εἰμι. Using his method, should this be "I have been the door/gate"?
John 6:35, "I am the bread of life", literally ἐγώ εἰμι. Again using his method, should this now be "I have been the bread of life"?
John 8:12, "I am the light of the world", again ἐγώ εἰμι. So in his logic, "I have been the light of the world"?
None of that makes sense, and it's just where this kind of argument fails.