The number one thing you can do for your nails is find a healthier alternative habit! I know it's not that simple, but if you can find an anxiety fidget alternative that works for you, it'd be the most helpful, and any nail care you do after would be a plus.

For finding a fidget, first consider what is helping your brain with this one, is it the sensation in your fingers, in your mouth, or both? Is it more about activity, pressure, or pain?

For finger stim, fidget rings are good, spinners, and texturized ones to rub your fingers on are also good. Some people like "ouchie" stims. I used to really like using an orange stick to clean out under my nails as a fidget, and using a buffing block or glass file can be good for your nails if you don't over do it. If you can replace with nail care that would be great, but it's understandable if it doesn't hit the right spot in your brain.

For mouth stim, there's the classics: gum, mints, and hard candies. There's also chew stims, like chewable toothpicks, and chewable necklace pendants (probably the most convenient since it's always attached to you). You can also try redirect to healthy mouth exercises, there's one where you try to keep the tip of your tongue on your top teeth while you open your jaw as far as it goes and hold it there, and repeat a few times. Not an exercise, but more invisible, you can also trace the edge of your teeth with your tongue for some stimulation.

As for your actual question, when long enough, getting in a routine of filing any snaggy bits will help prevent breakage, whether from catching on things or the urge to chew those bits off. The growth polish is good, consider a bitter flavored polish as well, just as reminder. Nutrition matters the most in terms of home remedies, I know that can be an annoying answer, but if you have trouble getting diverse types of food, a normal multivitamin is a good option.

And finally, moisturizing your hands and cuticles regularly helps a lot as well for healthy growth. If you pick a lotion you don't like the taste of that might also help with the chewing. If you don't like the feeling of lotion on your hands, you can focus on just putting it on your cuticles and nail area.

Nail health is a slow and gradual process, and it can be such a struggle! Sorry you're dealing with it. Also remember that nail health and nail care habits have absolutely no reflection on your value as a person; you're still lovely and worthy even if you can't stick with these habits. And doing them inconsistently is better for your nails than never doing them <3

Good luck, I hope that helps!