Yes, that’s scaling the game canvas. Try without that to see if it makes a difference.
I don’t think the scaling values (0.1, 0.2, 0.4) will make much difference below 50%.
Yes, you would create a multiframe texture — texture atlas in Phaser terms. But test this first to see if it looks any better before you go to all that work.
I realized it’s not really practical to change frames (sizes) during a scale tween. You would change at the end of the tween instead.