The cracks had occurred off of where the hole was drilled through the x member. Life and death....probably not. Seems more like a progressive fatigue around that weakness in the steel in conjunction with the flex of the frame at those end points on the x member...
Keep in mind that Im not trying to sway you one way of the other.
I can imagine some cracks there over time.
I'm here for your (and others) input since your project has similarities to my rusty old tractor.
