To my knowledge, japanese weapons never used a curved handguard. The image the comes to mind when I look at 刀 resembles more the hilt of a cutlass than a katana.
I imagine the guard here is a straight horizontal part (with the right leg being a knuckle guard, and the left one as a handle).
I don’t think that the wording should be changed. You’ve came up with a mental image in the end, so good for you, but there’s no need to impose your personal vision on others.
Here’s how I look at it. 力 is supposed to be a steroid pumped guy flexing his arm–meaning ‘power’. I just imagine someone came along and cut his steroid injected head off with a sword (刀) because he was a short tempered jerk that bullied everyone. That’s why you don’t do steroids folks, lol.