Could the Moon have been closer to Earth?

Yes, yes, and yes. Tidal forces are slinging the moon away, currently at a rate of about 3cm per year. The process is slowing as it gets further away, and varies with changes in the distribution of mass within the earth. read more

When the moon formed, it was much closer and Earth rotated about once every five hours. At that time, since both were molten and closer together, tidal forces were much, much stronger. Once they cooled off, the process essentially stopped until earth’s oceans formed. Today, it is the squishy oceans that account for about 90% of the effect. read more

The Moon probably couldn't have formed closer than 3 Earth radii because tidal forces from the Earth would just pull it apart again, and it is unlikely that the impact could have ejected material further than 5 Earth radii. read more

Now, moving the Moon closer to the Earth will increase the gravitational exertion of the satellite onto our planet. If the satellite were slightly closer, the tidal bulge would grow. Low tides would be lower and high tides would be higher and any low lying coastline would be flooded. read more