>sun loses mass leaving Earth beyond its grasp

This is incorrect. The Suns expansion does not equate to mass loss. Cosmologically its mass will have not decreased that much (which is what will determine where Earths orbit is) but it'll be fusing helium into carbon which is a hotter more energetic process and so the outer layers of the star will get pushed out and the star expands. Earths orbit won't change much however the Suns radius will expand to near or fully envelop Earth.