As a test…
Try creating a new product with one option - size (small and large) and select all the "update all options" check boxes for the areas that will remain the same in all products and save that.
Than find the product in Admin and choose update.
Assuming for the moment that the only differences will be size, price and SKU - choose the next size option from the drop down and after it refreshes, change the SKU and the price and choose "update" at the bottom of the page and see what the results are.
Let us know