Really recommend a trip to a chiropodist that can show you how to keep them clean. It's not nice but if you remove the 'debris', continue with the tea tree and let the air get to them, it will take time but I'm certain things will improve.
I had to scrape the sides of the nails, file down the thickened nail and generally keep removing the affected crumbly material. Eventually the fungus 'lost its grip'. I also only used the same towel to clean feet with and patted them dry, if you rub I was told it sends the fungus deeper.
On another note, drinking apple cider vinegar might take care of any candida you might have in your system that might contribute to the happy home for fungus.
it's a real pain to deal with