I am sorry to tell you that your cracks will never go away. They normally open up in the Summer and close up in the Winter.
The only way to forever fix it is to do some foundation work and shore up with concrete piers and footings and use the jacks like Ram Jack uses. You could maintain moisture around those piers with a soaker hose or lawn waterer. The ground is loosing water which causes it to compress and the foundation falls.
I am going through a total foundation re do myself. I live in Dallas, Texas.
Now, there is the fiberglass stretch tape that is supposed to give alittle. You could try that, but I have not had much luck with it actually streatching when the walls shift.
Just fill it up with latex paintable caulk in the summer and the fall when it closes, scrape the caulk away and paint again.