Kaido's haki increased because he was a natural alcoholic. What you're saying is peak headcanon. Bajrang gun, the fist that scaled an island, finished the job. Unless you mean to tell me his awakening was useless.
Strongest person in verse you mean who? Wasn't Roger for sure since WB is the one considered the strongest since Roger era. But you are most likely right since Ryuuma was the strongest human on earth and doesn't seem he had any DF.
Shanks is not top of top tier. No one ever praised Shanks strength. People always praise his crew as a whole.
G5 relied on his abiliti to make a huge fist in order to defeat Kaido. And even that wasn't enough since he was losing until Kaido started to talk. G5 relied ultimately on plot armor.
1. Silly point since whitebeard also needed haki to clash with rodger.
2. Kaido was on the same crew as whitebeard yet still revered rodger as the strongest between the two.
3. Shanks isn't the top of the top tier? Cool. By your logic but definition mihawk or kaido are. Guess what kaido stated "haki >> all". Mihawk as shown also doesn't have a devil fruit. So it's still "haki>>All"
Again dumb point. Luffy relied on the raw power of his fruit. However all the gimmicks used was still ineffective until he used coc infusion. Luffy was at the pinnacle of power and still had to rely on coc why because coc only becomes stronger when the user himself becomes stronger as stated by Rayleigh