Q. If the Earth truly did expand, wouldn't gravity have decreased, not increased as you suggest?
A. The smaller moons and rocky planets are all smaller in size and mass with a reduced gravity. Look at the Moon and Mars for example. The Moon has a radius of 1737 km with a surface gravity of 0.16g. Mars has a radius of 3,396 km with a surface gravity of 0.38g. Why would you think the ancient smaller Earth would be any different?
We can calculate gravity on the ancient Earth using Newton's formula to show that surface gravity will remain directly proportional to radius - assuming that density remains constant. So an ancient Earth with 50% current radius would have a surface gravity 50% of the Earth's current gravity if the density remained constant.