The flat range swells to everything suited and connected — the button prints deep by keeping ranges wide and pots young.
The 3-bet range condenses toward hands that welcome a giant pot; almost everything else that plays well flats. Bloated pots with dominated hands are how 500bb stacks vanish.
Button against a middle open — wide enough to attack, strong enough to respect. The classic mixed defense: polar 3-bets over a broad flatting core.
Assumes a ~4bb open; 3-bet to ~3x the open in position, ~4x from the blinds — larger as stacks deepen.