Prodigal Son (That's what I'm talkin' about....most of it, anyway, with some variation)
GLADIATOR
If God's existence was PROVEN TO BE TRUE scientifically, then the next step would be how to develop the means by which all people would learn how to communicate with Him/Her.
If God's existence was PROVEN TO BE TRUE because He/She personally revealed Him/Herself to the physical plane, then the next step would be actual communication as to how the earthly kingdom is to be set up and administered.
[1] How would that change reality as we know it? Reality wouldn't change. Our awareness of it would.
[2] Would it create a society where we no longer have free choices? No. It would create a perfect Government based on True Liberty and Justice for all. Each individual "sits under his own vine and fig tree" in that he/she is independent and takes care of their own needs. If there were no law other than "love God with all your heart, soul, strength, and mind, and love your neighbor as yourself", perfection would be achieved.
[3] How about personal responsibility? You will always be accountable.