The vacuum,an Idea

May I first of all offer my sincere appology for my absence of late,my illness prevents me from attending my local library to use the computers.but I am glad to have provoked a livelly discussion.to question the world around us. I will ask you this, the sun by human standards is a huge astronomical body, but its sphere of gravitational influence is many hundreds of astronomical units in diameter,considering the sun is regardless of its mass and core density is I would say at least ninety five percent empty space, is the mass of the sun entirely responsible for the dimensions of the sphere of influence, or is it in part generated by the pressure of the expanding vacuum impinging upon the particles of the sun and so in effect partly powering the size of the gravitational sphere ? Is the idea that the universe is expanding rather like a baloon entirely correct with the violently expanding vacuum not impinging itself in some way against the matter external to it, if not I find it dificult to explain the Inflationary Theory and the creation of the objects we observe.