I'm not 100% sure, so perhaps other teachers will comment, but here's what I think: glow on = caused by something external "As he approached the end of the tunnel the first thing he noticed was a slight glow on his skin." glow to = caused by something internal "The yellow glow to his skin and his eyes told me that the problem was his liver." I do think there is a sort exception to this rule (the rule I created above), because people often use 'glow to' when the glow is caused by some sort of tanning product or process... is that internal or external? I don't know. I'm not a scientist. I think people choose 'glow to' in this context because it seems more natural... maybe?

Number 2 sounds most natural to me~! ^^

"To" is correct. It reflects a quality of the skin and not something that is "on" the skin. And that's just the way we say it.