It can. Have a podiatrist check it. Filing down the toenail can help get rid of the environment that fungus likes to thrive in. Just make sure you don't go too deep and damage the bed. Anti-fungal medication can be used in the form of topical or oral forms to work adjunct. Keep in mind, once you clear the fungus, it is important to avoid re-infection!
Yes. The thinner the nail the better penetration the medicine will get into the nail. That being said do not thin it to much. No treatment is 100% effective but many do help.
Yes. . Fling off the top layer of the nail will help topical anti fungal medicines penetrate a little better.