And if you want to know when specific bonuses kick in good news Serebii is the only site that bothered to track this:
https://serebii.net/swordshield/happiness.shtml
tl;dr
200-229 adds a "survive KO" chance
230-254 adds 20% exp gain, chance of recovering from status
255 adds chance to dodge an attack and raises crit ratio by 1 stage.
https://serebii.net/swordshield/happiness.shtml
tl;dr
200-229 adds a "survive KO" chance
230-254 adds 20% exp gain, chance of recovering from status
255 adds chance to dodge an attack and raises crit ratio by 1 stage.