Hey hey! Thanks for playing :)
Achievements are earned based off of eating different races and similar actions. They're mostly there to list out all the races to find, and earning enough will allow you to boost your starting stats.
Yes to the disappearance. There's not an easy way to process what happens next, and usually the enemies would just eat your abandoned friends anyway.
Skinny/Chubby/Athletic can sometimes give a SLIGHT boost to starting stats, but nothing meaningful. It's flavor.
Wait, you brought the baker chocolate but she couldn't eat the chocolate? I've never seen that before!