Quote by 256bits
...again from another assumption that the table weight is evenly distributed, and that the compression of each leg is also proportional to one fourth od the table weight, again from an assumption that each leg is completely similar to all the other three.

I don't follow how the weight of the table or distribution or size of each leg would affect this.
If he manages to level the tabletop, and sets the concrete. What's the problem?
Quote by 256bits
I would conclude that this method would result in a table that is nearly level, with no method of determining how near to level the table would be.

You'd use a level on the table top.