RMCHRGR, I see some of your confusion in what you are saying.

A) what you have is a 2 pole switch (4 post/connections) which is a DPST. think of poles as switch contacts.

B) The small pole of the switch you have is only rated at 20amps, this will not handle your ALT output. But will work to break your MSD small red (turn on)input or other small loads like relays

C)The more relays and connections you have the more places it has a chance to fail. Which normally happens when it is most inconvenant.

D) Any time you have a relay energized it will draw power. So if you wire a relay that is controlled by your disconnect switch you will have to turn off the switch when the car will set, or it will drain the battery over time.

There are alot of ways this can be done. Try to make it simple.