Lateral cracks are almost always a non-issue, especially that size. The only hitch is that as it grows down and reaches the bottom, the area just below can tend to break off a little, but usually doesn't cause any lameness or further issues. It could be an indication of founder/hoof issues, especially if you see several of them, but in general, they are nothing to worry about.
Strangles, once they have it, is less of a threat in the future. I think you get better future immunity from actually having it than from the vaccine, at least in my experience, but I'm not a vet, and most would probably still tell you to vaccinate for it. I think they pretty much carry it while sick with it, then it's not apt to spread again, but hopefully Ryle will see this and put in her 2 cents. However, ranches or other facilities that have an outbreak may have future outbreaks when conditions are right, but that is old information, and possibly inaccurate. =/