Thanks for playing! :)
The weight is pretty unbelievable, but that's on purpose. Later in the game, it becomes apparent that the player's being influenced, and probably being corralled into more misadventures despite being a weight where they shouldn't be able to anymore.
Every character will be able to gain weight by the time the game is complete in mid-late 2021. Additional weights may be possible, but I've not figured out how I want to implement them yet. Having an NPC live with the player is already in the idea pool for the game, and there's a chance this'll be a thing one day. In terms of actual reproduction, etc, I'm afraid there are no plans for that.
The main pieces of upcoming content are the weight gain routes for all the characters. There's a broad number of secondary objectives, but it's all Patron-voted so even I don't know what they are yet!