backset of door width compared with 40-028

Thanks for posting! By back set, do you mean the face of the door where the lock is being installed? For storm doors I have worked on, the face of the door is normally 2" wide, while you have only a 1-1/2" face. Looking at the 40-028 In-Swinging Door Handle lock's dimensions (see below), you will need 7/8" from the edge of the door to the center of the lock. Since the lock face width is 7/8", I'm figuring you should have 1/4" on the back edge of the lock. There would be no room for error here.