I gotta preface this with the fact that it's always exciting seeing interest in Mewtwo, as it's rare that people give him the time of day. I very much want to encourage you to keep playing Mewtwo, as I think he's actually quite a good character and people simply fail to realize it. Now to talk about your guide.
That is more of a snippet than a guide. It simply doesn't cover much about Mewtwo, his moveset, his tools, and how they relate to his matchups. I've written in depth recently about SBC (shadowball charge) in which I have written more one that one subject than you have in your guide about Mewtwo. If you want to write a good guide, you have to simply invest more time into it, and it's also good to reach out to other players for information and advice.
An example of a guide I wrote back in 2013 :
https://docs.google.com/document/d/1Daf_Dqod1HoMj7L26ITeUM-xKUKhfxh2vJLWOl2N0C8/edit
That guide, while a bit unconventional, is quite thorough and covers a lot of material.
Another thing I'd point out is that I don't think Mewtwo actually struggles that much against the top tiers. He actually can handle them quite well. I might be alone in saying and thinking this now, but I really think that people overestimate Mewtwo's weaknesses and underestimate the versatility of his moveset to deal with his opponents' tools and to hide his own weaknesses. If you are interested I can upload some recent videos of me dismantling good Marth players on netplay to show as examples for how Mewtwo can adapt to a matchup that has long been considered free for Marth.
