I hope that tree is a Trident Maple as I surmise it is!!
Without going into alot of argument here other than getting the stones from around the basal area and the rocks out of the roots, the tree should survive and hopefully callus off the crack. There is deep roots supporting this tree below...........evidently the previous owner didn't allow for expansion of the trunk. You guys have had plenty of extra rain to cause the influx of more leaves this season. This will lead me to think that as SmallAxe mentioned as excess leaf growth will lead to sudden leaf drop as the heat packs on. This is natural of a trees defense against moisture retention and sugar production. The rains have depleted some type of nutrient deficiency only detectable by a soil sample and tissue sample. If you are planning on mulching around that tree........extend the bed to the end of the drip line. If no one else will admit this is the best thing to do, then the Arborist's Society is losing ground on educational and professional practices taught to its Arborist's. I gave up on tree surgery several years ago because it was too impractical around my area. With the big ticket store's offering free replacement of dead and dying trees and shrubbery with the proof of receipt, the public has become lazy and irresponsible. If it dies........someone will replace it!!!!For Free!!
The photo of the root cutaway where you removed one of the face stones......shows excessive root massing. These are a small part of the feeder roots..they are the small ones that draw moisture, release toxic byproducts and absorb nutrients from the subsoil and topsoil. If these things are restricted and can't find the nutrients on top as they are used to doing, the tree will suffer. It is no different that spoon feeding any type of grass or shrub and then suddenly taking away the food after all the roots are used to being fed.