Can osteochondroma cause stress # in a similar location? If so will healing time of the # increase?

Yes and maybe. It really depends on the size and location of the tumor. The tumor itself can fracture, or the bone above or below it can fracture if the tumor causes enough deformity. If the tumor was surgically removed from a weight-bearing bone, there may be a defect in that area which is prone to a stress fracture. Healing time is very individual. Follow your ortho's instructions to heal quickly!
Yes. Oteochondroma is condition called benigen tumor of the bone start early in life and stop growing with bone maturity (17 years).Some the patient have one or more than one, usally located arouund the jiots area but could found in other locations, I do not know what you by stress, please explian?