I need to create a grid of points within a given area so that each
point is 75m across the ground from any other point
There are cases where this may be impossible mathematically. For illustration purposes, if you are laying a fishnet on the curved 3D earth surface with neighboring points 100 km apart from each other (about 1 degree apart) and in alignment with the lat/long grid.
If such a regular fish-net (in terms of ground distance) exists, and if you count the number of squares at the same latitude, then there is going to be about 360 of those squares on the equator, while there is going to be about 1 square at the north/south pole (considering the length of the parallel lines in those regions).
What this means is that you have to shift the points around, and the result you get is not a regular fishnet anymore (at least not something like the rectangular fishnets you can create on a plane).
Practically, I think if you write an algorithm for this (or do it manually), you often will have to finesse point locations to satisfy the distance requirement. There is no guarantee that you can always find the next point satisfying the distance requirement or that such a regular fishnet on the curved surface exist.