It's my understanding that you should not plug anything into the cable pre STB or SACM as this is against T&C and can upset the network for all other users on your segment and screw up the SACM / interactive downstream.
If you want to distribute analogue chanels you should take the pass through output of your STB and then distribute / amplify (if necessary) this output.
Hopefully your STB has pass through. If it does you will have a coax going into the back of your TV from the STB that shows 1-4 and the cable box output. You can do what you want with the output from this cable.