Interesting, but there are few points I disagree with like Zeref isn't stronger than Irene and August as they wouldn't follow him if he wasn't stronger. He is and could do attacks as strong Acnologia or even a bit more as Acnologia vouched on his power when they meet up and that is before FH. Pretty sure those two on their final forms are multiple continent or better yet given their Time and Space could destroy universe in that same level like many in Naruto and Bleach scale as well, but I do acknowledge about Bleach and Yhwach is only thing I see as most difficult, but let's say they all are prepared and planned ahead on knowing each others abilities, who you think will still win?
August followed him because he was Zeref's legit son
Irene followed him because she had a place of belonging
Its not all down to strength
If FH Zeref was as strong as you think, he'd have never lost. Fact is Natsu won the fight as a high tier. Power of friendship blabla I know, but Zeref, with the power at his disposal, if he was truly godly, would never have even taken one attack head on. Natsu would never even cause any damage. Zeref in base is much weaker than most people think he was. FH was only a buff to his speed and a few new spells which didn't make him any more powerful in any regard other than his evasive abilities.
Irene's Universe 1 affected the country of Fiore. Thats the biggest scale thing we've seen in FT and that magic didn't even pertain to any form of destructive power, just massive range. In terms of pure destruction, the top of the list is Acnologia "destroying" Tenroujima, which is a very small island.
With knowledge of Yhwach's ability? That makes no difference. Even if you took away an enormous advantage Yhwach has because of Almighty by giving everyone the knowledge they need straight up, he still knows how they will act and what they will do. He still knows exactly how to counter it. To defeat Yhwach, you need to literally exhibit power that surpasses his own many times over, to the point where he can't actually do anything about it; you'll only see that when you get to top tier Toriko characters or namek saga characters from DB.
The whole point of Almighty is you cannot counter it. Change any measures youd like, he still wins.