I suppose it could work for people who are athletic and single, such as typical college students and recent graduates. I did once live in Boston without a car.

Outside of Paris is supposedly not very French anymore, and not very safe. It doesn't seem like a place you'd willingly live with kids. Maybe you mean really far away, far beyond the suburbs.

Your culture goes extinct if you don't make more.

I have 12 people, including one who is 198 cm tall and still growing. Standards for "decently" vary; large families normally cram people into a normal-sized house (140 to 280 m²) almost like the pre-boomer generations did.