Im fine with MC being fat and changing over time. I can understand Girls from the household where MC lives might be interested in MC, because even though he doesn't look like an attractive type. The girls might like him because he is respectful and caring in his own way, even if he's a loser in everyone else's eyes.
As for everyone else, his female best friend had a bad past, and MC was the only one who cared enough to understand her.
As for all other women from school to the gym, I agree it seems weird to me. Unless explained later, MC has some Aura (scent) that attracts all women we dont know yet, making it more believable.
For the Emma and random handjob scene with the guy, I agree, hope Dev goes back and makes it avoidable, in most romance-harem type players dont want it or see it, unless it's non future Li's dont care about, unless he's planning on adding more stuff like that, for his "voyeurism, sharing" players.
Overall, I think it's an okay story, I dont mind MC being fat, and improving himself.