Seems as though you can't programme as above
So you need to use
0v
+12v
Then the relay for the bell trigger , which drops bell trigger to 0v when siren goes
The tamper could be used on a zone in defence mode , look at page 11 , although not a tamper it can act as a 24hr armed zone , but you would have to mess around to make it work
Assuming that zone on the back is programmable it might work , you also have an onboard relay which could be used for a bell trigger depends on what it does
Common problem on these are the spring , users mess around with the cover and screw and realise it was the spring after all
Not surprised by what you're saying you didn't need to do half of what you did but it is how it is, you damage the case
Be gentle adjust spring and your done, or call an engineer... ...