Handle pair, 40-101

I am having trouble with the lock set from a storm door that was installed about 15 years ago because it won't stay latched. It is a combination of problems, with the spring that pushes out the latch seeming to have weakened over time and there being no apparent way to replace that spring. Now, because of the effect of gravity from the heavy handles with the original lock set, the latch does not want to protrude out as far as it should. The 40-101 handles seem like they would be a smaller, lighter replacement handle that would help the situation, and all of the dimensions match up, except the 11/16" diameter. That diameter on my handle appears to be about 1/2", and that is about what it looks like in the picture for the 40-101. Any chance that dimension 11/16" dimension is wrong?

The faceplate length is 7.75" coverall. The outer holes screwing the faceplate to the door are 6.25 on centers. The inner holes for securing lockset to faceplate are 5.125 on centers. The lockset dimensions are 5.75 x 1.6875 x 0.5. I would like to replace the spring but don't know the right spring, or how to do it. I can't find any manufacturers info. The lockset is about 15 years old.