Brake Fluid Leak problems of the 1996 Dodge Ram 1500

I was traveling to town and as I entered the town as I started to brake I could feel that my brake pedal was feeling spongy and the pedal seemed to be going to the floor. I felt as though 90% of my braking was gone. I was able to stop safely though I had very little braking. I felt that I could not stop safely in an emergency. I returned home very carefully at slow speeds. After looking my vehicle over I saw that all the brake fluid was gone from both the front and rear compartments of the master cylinder. Under my vehicle it seemed to be wet from brake fluid between the fuel tank and frame rail where the brake lines run. The brake lines had rusted through and leaked out all fluid. I feel there may be 2 dangerous issues. 1 that if the front or rear line leaks, the remaining chamber of the 2 chambers in the master cylinder should not loose its fluid. This allows limited braking with the brake section that has not lost its fluid. The 2nd issue is that the rear brakes line runs in the frame rail between the fuel tank. The fuel tank is constantly sweating on humid days which subjects the brake lines to constant rusting. Until they rust through. I may take several years. With the brake line running in the vehicle frame rails very close to the fuel tank you can not easily see if any rusting has occurred until its too late. I have also had another vehicle of another manufacturer also rust completely through loosing all brakes. I feel any vehicle that has a fuel line in the frame next to a fuel tank will also rust through. Because of the fuel tank sweating.