I actually did not check your file then (and still did not) and those are just general remarks for how FreeCAD works. Recomputation of the document happens in order of dependency. So if object 2 is somehow dependent on object 1 first object 1 is recomputed (if needed) and then object 2. And if you somehow manage to make object 1 dependent on object 2 this will trigger recompute of object 1, then object 2, object 1,... dependency cycle.
Spreadsheets are treated as single object in that dependency order. So is the sketch changes this will trigger change in that spreadsheet cell, the whole spreadsheet object will recompute, sketch depending on it will need to also recompute -if it is used in the first sketch this will cause dependency cycle.