Just because your grommets are not parallel does not mean you’re lacing incorrectly.
It’s the corset that is not right for your body.
According to Lucy Corsetry, “Wearing a corset with an uneven gap doesn’t mean you’re wearing the corset incorrectly – it’s not the fault of the wearer, they are lacing it so that its comfortable and its not going to cause injury.” – Lucy Williams
If your lacing gap looks like an A, small on top & large on the bottom, it might indicate you need a larger hip spring; the corset is too small on your hips.
If the corset looks like a V, and the lacing gap is large on top & small on the bottom, then you may need more room in the rib area, or a larger rib spring.
If your lacing gap looks like an oval, small on the top & bottom, and larger in the middle at the waist, your corset size may be too small for you. If the lacing gap looks like an hourglass, large on the top & bottom, but at the waist it’s practically closed, then the corset may be too large.
I would suggest keeping the lacing parallel as best you can, because you don’t want to hurt yourself.
And if you force the corset, it could break.
The way to get parallel laces is to get a better corset.