Your forced perspective is actually correct in that you are drawing the front and top of everything in block form. Whats probably throwing it off a bit is the park bench, on the bench you're using a true perspective by slanting the sides of the bench seat. So the two styles contradict one another.
The trunk of that tree is REALLY straight and crisp, try varying the line a little to create a more organic quality. You might also try suggesting some leaves here and there on the tree's canopy. You have great form but drawing a few clusters of leaves will really sell it.
Also, your wood floor looks more like a woven basket. The shading on the boards makes them look more rounded than flat.
A little more texture in your grass could go a long way =)
Just suggestions of course, all in all you have lots of nice stuff happenning here.
The perspective is like an optic illusion. Is it straight from above or flight view?
The furniture suggest that its the second but the the dog suggest the first. And then the tree and the dog in the back is completely flat like its viewed from the side. Also the cabinet and the stone could have some more detail.
Sweet, this is a great idea and really well done!