(20 points) Read the material and answer the questions:
As shown in Figure 5, the shapes of rhombuses, rectangles, and squares differ. We refer to the degree of similarity between these shapes as "closeness."
When studying closeness,
the closeness of similar figures
should be equal.
(1) Let the two adjacent interior angles of a rhombus be $m^{\circ}$ and $n^{\circ}$. Define the closeness of the rhombus as $|m-n|$. Thus, the smaller the $|m-n|$, the closer the rhombus is to a square.
(i) If one interior angle of the rhombus is $80^{\circ}$, then the closeness of the rhombus is $\qquad$ ;
(ii) When the closeness of the rhombus equals $\qquad$, the rhombus is a square.
(2) Let the lengths of the two sides of a rectangle be $a$ and $b$. Define the closeness of the rectangle as $|a-b|$. Thus, the smaller the $|a-b|$, the closer the rectangle is to a square.

Do you think this statement is reasonable? If not, explain why and provide a reasonable definition for the closeness of a rectangle.
(1)(i)20 (ii)0 (2)Unreasonable
In rectangles with side lengths of $a, b$ and $2a, 2b$, it is clear that these two rectangles are similar, but $|2a-2b| \neq |a-b|$.

The proximity of a rectangle can be defined as $\frac{a}{b}(a \leqslant b)$, then the closer $\frac{a}{b}$ is to 1, the closer the rectangle is to a square.