The perimeter of the rectangle is 64
It is always isosceles because it can be proved as follows:
The perpendicular bisector dissects the triangle into two, and it is the common side. Then each side of the bisector is 90 degrees, and the bisected to two equal sides, so the two dissected triangles are congruent, hence the original triangle is isosceles.
Top left -4,4
Top right 4,4
Bottom left -2,-2
Bottom right 4,0
You can prove the proofs by showing your work to prove the proofs.