Adding more alcohol(gas line antifreeze) won't help w/ alcohol fuel. Aviation fuel (100LL)has no alcohol in it, keeps forever, costs a little more, but safe.
I don't know what gas line anti freeze is but it's job is to absorb water in the fuel to prevent freezing in the gas lines. As I stated I've read that it's been successfully used to prevent phase separation. If the poster of that information was wrong I apologize for muddying the water but I've also not seen anything that says it doesn't work either.
