How long have you been OPing? I'd heard that OP plus this salt water gargle has accomplished that very thing for some people.
But really your condition is most likely systemic of some kind. It sounds like you have a lot of issues you need to work on and will probably need to chip away at them the best you can.
The good thing is while you are doing this or that cleanse you can OP through all of them. Here is a post I made awhile back and you can see I was in pretty dire shape also. I'm happy to say that I've never felt this healthy. I'm also amazed that this post was back in September. I've come even farther since. I've also added Iodine to my supplements and that stuff is amazing. I was terrified of it at first, but it's done so many good things for myself and my husband.
You are heading in the right direction. Keep going and read as much as you can. There are so many here who have at the very least helped their white tongues with various cleanses. I just know you can too.