The problem isn’t getting the value as much as transmitting it back to the blueprint.
Why not just go the other way around the problem?
Create a variable (game level is a good spot for this one) - pass the variable to the widget in BP, which will use it to offset the cross hair. Use the same value in your ray tracing calcs.
That way the value is not set in Widget and you won’t have to read it out either. (note -220 is probably not the value you want for the trace. camera position break vector, add to Z to offset up. You might need to transform this value that works in world space with unreal untis to something the widget can use.)