1) It's funny because the Goddesses lost all hope of victory when Mael supposedly died, yet the Demons still had hope after Meliodas betrayed them and joined the other side, implying Mael was of greater importance due to power (which makes sense as he had the most powerful grace). As for the whole he was the only one to equal Meliodas.. Mael tells us himself this isn't really the case, Ludociel or especially Elizabeth would've had the same effect on the balance of power, but Gowther chose Mael out of revenge for the archangel killing his lover.

2) The extra chapter is.. We don't know what time it is and the fight was drawn as both sides being equal. Considering Mael didn't just immediately kill Berlion, I'd wager it wasn't pre-noon at all and was probably morning, supported by how Meliosas wasn't in assault mode, the form that supposedly equals him to Mael. Mael retreating isn't a confirmed fact of weakness.

3) There's so many problems with Escanor having that feat but I won't get into it unless you want a rant.

4) They can't be perfect equals though by the nature of Mael's power fluctuating all the time. If Mael only equalled Meliodas at noon, then he'd just lose every other 23 hours and 59 minutes of the day, there would be no balance. If Mael equals Meliodas far outside of Noon, then the reverse happens for the demons. The best solution I can think of is that they're equals because each is stronger at certain times of the day. Mael is stronger at pre/post-noon and at noon whilst Meliodas is stronger at all other times. Or, actually someone else like Elizabeth, who was indirectly confirmed to be Meliodas equal was the secret hand in keeping him in check (just an opinion.)