Obligatory 'not a doctor'

The final options are surgery vs 'do nothing'. Onychomycosis (fungal nail infection) often doesn't need a treatment, unless you're immunocompromised it's just a cosmetic thing. Surgery, in this case, involves removing the nail, and killing the matrix, which is the nail bed. This means you won't have toenails anymore. This isn't a problem as we don't use our toenails, but some people will opt to apply fake nails for cosmetic reasons.

Missing applications here and there will have a negligible impact on your treatment, you don't need to worry about it. We would regularly tell people that if they're going on vacation for a week, feel free to paint your nails and stop treatment until you come back, then resume. Fighting nail fungus is a long game, it can take upwards of a year to knock those bastards out. As long as you're using the topicals >90% of the time, you have a good shot. That being said, even thebest treatments are only proven ~60-70% effective, but that includes the aforementioned "too far gone" nails trying treatments admittedly in vain.