Let's begin with #2: Baku didn't have to bet on Hal recovering his memories. He was simply betting on him to get the message "Hal 36". After all, he got it once before
Now #1 is harder to make sense of: After all, Baku really had no way of knowing how the upper floor is situated, therefore he really had no basis for believing the message actually reaches Hal. So it really was a crazy gamble. But at the same time, he also loses nothing with trying it (unless he decides to go with different scenario, which I cover below). Then I remembered Kaji's train of thoughts in chapter 454:
https://mangadex.org/chapter/869518/5
https://mangadex.org/chapter/869518/6
https://mangadex.org/chapter/869518/7
So if Baku didn't believe the message reaching Hal, didn't reserve 25 for the last round, but used it in the 4th round instead (and consider that Baku reserving air was indeed just a bluff) there are two possible situations:
1: Lalo only bets Ante and Baku loses
2: Lalo bets more and Baku wins
Baku going with #2 would be essentially be him betting on Lalo not reading the situation correctly and calling/betting in the 4th round. Let's say Baku decides to go with this, but instead of betting right of the bat, he does more Baku-like move and sneakily checks, baiting Lalo to bet something and than raises him. Rings a bell? That's right, we sort of got this situation from Lalo's perspective in chapter 456. Remember that panel which confused the hell out of us?
https://mangadex.org/chapter/879847/11
https://mangadex.org/chapter/879847/12
Imagining that, Lalo didn't took the bait and bet just 1 Air Bios. If the author really included this to show what would happen if Baku chose to go this way, then holy shit! That's crazy!
So basically instead of believing in Lalo's "weakness" Baku decided to believe in Hal's strength and go with a crazy gamble with very low probability of success. But to quote Tokuchi Toa: "Low probability means, it's not 0".
To sum it up, from normal persons view, Baku was in a desperate situation and decided to rely on some crazy luck to achieve victory.
But from Baku's point of view, it was just another gamble