Chassis battery disconnect revisited.

It sounds like the chassis disconnect relay may be DE-energizing when you actuate the switch but the relay contacts may have arced and welded together. First put your hand on the relay and have someone else flip the switch to make sure you are working with the correct relay, when the switch is activated you should feel a pretty good thump. After verifying you have the correct relay and the disconnect switch is activated take a volt meter and read the voltage on the large terminals both sides. You should read battery voltage on one side (12.4-12.6 volts dc) and zero volts on the other side. If you have voltage on both sides then read the voltage to the small terminals. Both of the small terminals should be zero volts ( some relays have only one small terminal others have two. On the relays with 2 small terminals one wire comes from the switch and the other to ground, relays with only 1 small wire are internally grounded and the single small wire comes from the disconnect switch). Using your volt meter determine which wire comes from the switch and disconnect it, if you then still have voltage on both sides of the large terminals then the relay contacts have welded together and needs replacing.
I know this is long and may be hard to understand so feel free to PM me and I would be willing to talk to you on the phone. KDK