you say the rust is right throu, these are the areas that you need to cut out and replaise asap, the rust only bicums wors and fast. I segest these areas get first attention. If you can get another section and replace the hole thing. In too three years it might have spread too the chessy, and that is so unnesesery, many prob too.

I understand the money isent allways there, but youll save alot in the long run.

(Only my expereiens, my opinion)