(Ⅰ) Since the length of the major axis is 8, we have $2a = 8$, thus $a = 4$. Without loss of generality, we assume the foci of the ellipse are on the x-axis, so the left and right vertices of the ellipse are A(-a, 0) and B(a, 0), that is, A(-4, 0) and B(4, 0).

Denote point T on the ellipse as T(x, y). The slope of line TA, $k_1$, can be represented as $k_1 = \frac{y}{x + 4}$, and the slope of line TB, $k_2$, can be represented as $k_2 = \frac{y}{x - 4}$. Given that their product is $k_1 k_2 = - \frac{3}{4}$, we get $\frac{y}{x + 4} \cdot \frac{y}{x - 4} = - \frac{3}{4}$.

Solve the above equation, and we have $y^2 = -\frac{3}{4} (x^2 - 16)$. Substituting $a = 4$ into the ellipse equation and solving for $b^2$ gives us the ellipse equation: $$x^2 + \frac{y^2}{\frac{16}{3}} = 16$$ or simply, $$\frac{x^2}{16} + \frac{y^2}{\frac{16}{3}} = 1$$.

(Ⅱ) When the slope of line PQ exists, let's assume the equation of line PQ is $y = kx + 2$. Points P and Q on the ellipse can be denoted as $(x_1, y_1)$ and $(x_2, y_2)$, respectively. By substituting $y = kx + 2$ into the ellipse equation, we obtain a quadratic equation $(4k^2 + 3)x^2 + 16kx - 32 = 0$. From this, we have $x_1 + x_2 = - \frac{16k}{4k^2 + 3}$ and $x_1 x_2 = - \frac{32}{4k^2 + 3}$.

Therefore, $$\overrightarrow{OP} \cdot \overrightarrow{OQ} + \overrightarrow{MP} \cdot \overrightarrow{MQ} = x_1 x_2 + y_1 y_2 + [x_1 x_2 + (y_1 - 2)(y_2 - 2)] = 2(1 + k^2) x_1 x_2 + 2k(x_1 + x_2) + 4 = -20 + \frac{8}{4k^2 + 3}$$.

The value range of $$\overrightarrow{OP} \cdot \overrightarrow{OQ} + \overrightarrow{MP} \cdot \overrightarrow{MQ}$$ is $-20 < \overrightarrow{OP} \cdot \overrightarrow{OQ} + \overrightarrow{MP} \cdot \overrightarrow{MQ} \leq -\frac{52}{3}$.

When the slope of line PQ does not exist (i.e., the line is vertical), the value of $$\overrightarrow{OP} \cdot \overrightarrow{OQ} + \overrightarrow{MP} \cdot \overrightarrow{MQ}$$ is $-20$. Combining this with the previously derived range, we can conclude that the range of $$\overrightarrow{OP} \cdot \overrightarrow{OQ} + \overrightarrow{MP} \cdot \overrightarrow{MQ}$$ is $$\boxed{[-20, -\frac{52}{3}]}$$.