I have also read that adding salt, can make nitrites less toxic for your fish. I have not tried it myself, so I will leave it open for others to comment, if the benefits of adding salt would out weigh the negatives.
Sounds like you are doing all you can. Like Angel said, its impossible to put a date on when your tank will be cycled. All you can do for now, are your daily water changes and keep your fingers crossed for good test results. I can feel for you. Dumb me, did a fish in cycle on my 210 gal tank. I was able to seed the tank with some media, but still needed to do daily 50% water changes to keep ammonia and nitrite as low as possible. Talk about a high water bill that month!