Answer: 150

Solution:

By power of a point, $AP \cdot AQ = 3 \cdot 12 = 36$ and $CQ \cdot CP = 16 \cdot 25 = 400,$ so the tangent lengths from $A$ and $C$ are $6$ and $20.$ The tangent point on $\overline{AB}$ is $6$ from $A,$ hence $AB - 6$ from $B;$ equal tangents from $B$ put the tangent point on $\overline{BC}$ at that same distance from $B,$ so its distance from $C$ is $BC - (AB - 6) = 20,$ giving $BC = AB + 14.$

Let $\angle BAD = 2\theta.$ The center lies on the bisector of $\angle A$ with the tangent length from $A$ equal to $6,$ so the radius is $\rho = 6\tan\theta.$ The circle is tangent to both parallel lines $AD$ and $BC,$ whose distance apart is $AB \sin 2\theta,$ so $AB \sin 2\theta = 2\rho = 12 \tan\theta,$ which simplifies to $AB \cos^2\theta = 6.$ In triangle $ABC,$ $\angle ABC = 180^\circ - 2\theta$ and $AC = 3 + 9 + 16 = 28,$ so the law of cosines gives $$\begin{aligned} 784 &= AB^2 + BC^2 \\ &\quad {}+ 2 \cdot AB \cdot BC \cos 2\theta. \end{aligned}$$ Substituting $BC = AB + 14$ and $\cos 2\theta = 2\cos^2\theta - 1,$ the $AB^2$ terms cancel and, using $AB\cos^2\theta = 6,$ the equation collapses to $24\,AB + 336 + 196 = 784,$ so $AB = \frac{21}{2}$ and $\cos^2\theta = \frac{4}{7}.$

Then $\sin 2\theta = 2\sqrt{\frac{3}{7}}\sqrt{\frac{4}{7}} = \frac{4\sqrt{3}}{7},$ and the area is $$\begin{aligned} &AB \cdot BC \sin 2\theta \\ &= \frac{21}{2} \cdot \frac{49}{2} \cdot \frac{4\sqrt{3}}{7} \\ &= 147\sqrt{3}, \end{aligned}$$ so $m + n = 147 + 3 = 150.$