When I use any GUI scale lower than 6 or Auto (on a 1440p display), the Halo HUD isn't aligned with the crosshair:

(and with GUI scale 6/Auto:)

To confirm it's not any of my mods, I made a new installation with just these mods, and it's still off-center:

My settings:

Ah heck, centering things is always a mess. I must have broken it while changing the way I draw the halos... thank you for the detailed report.

The underlying problem is that the crosshair is not centered either, see https://bugs.mojang.com/browse/MC-157252

Workaround: this mod seems to make the crosshair properly centered(?)

Alternatively, DynamicCrosshair can also center the crosshair now.