设函数\(f\left(x\right)=k{a}^{x}-{a}^{-x} \), \((a > 0\)且\(a\neq 1)\)是定义域为\(R\)的奇函数.
\((\)Ⅰ\()\) 求\(k \)的值
\((\)Ⅱ\()\)若\(f\left(1\right) > 0 \),试求不等式\(f\left({x}^{2}+2x\right)+f\left(x-4\right) > 0 \)的解集;
\((\)Ⅲ\()\)若\(f\left(1\right)= \dfrac{3}{2} \),且\(g\left(x\right)={a}^{2x}+{a}^{-2x}-4f\left(x\right) \),求\(g\left(x\right) \)在\(\left(1,+∞\right) \)上的最小值。