I have a DSC LED5508 (z) home alarm system and have had it for many years

First problem:
Ph line stopped working... telecom guy came and said it was the alarm that stopped the ph from working so he disconnected the alarm from the ph jack point under the house somewhere... about a week later the keypad trouble light came on and the keypad started to beep twice intermitantly and this would happen any time of the day or night, when the alarm is armed or disarmed. When we are home we hold reset button down till it beeps once and then push the # button and the beeping would stop (sometimes for a short period and other times for days and sometimes the trouble light would go out or sometimes stay on)

Second problem:
The other day we had a storm and lost power to our home for approx 4hrs, I was by the alarm keypad when this happened and all the lights went out on the keypad which told me basically that the alarm battery was dead or near dead and needed to be changed. I left for work that morning and the power was back on so I held the away button down and set the alarm and went to work and purchased a new battery.
When I arrived home the alarm was armed and the trouble light was ON and I entered my 4 digit number but the alarm would not disarm (I tried this approx 4 times without success) I then accidentally stepped into one of the zones and set the alarm off.
I returned to the keypad and tried my number again but it would not shut off so I turned the maines off to the house and the alarm went silent.
I went into the roof space where the alarm control box is and removed the cover, pulled the fuse and disconnected both the posative and negative wires to the battery and returned to the HOUSE mains fuse board and turned the power back on.
I went back up into the roof space and connected the new alarm battery and replaced the fuse and refitted the cover then returned to the keypad, The alarm had returned back to how it was when I arrived home (armed light and trouble light were both ON), I entered my 4 digit number but the keypad stayed the same
(armed light and trouble light both stayed ON)

On returning to the control box in the roof space the alarm activated as I passed though one of the zones so I removed the box cover again and removed the alarm fuse and the alarm stopped so I then disconnected the new battery. The alarm is now totally deactivated

I also think the Installers number code was made up in his head and not a DSC code and he has since passed away

Please help to restore my alarm system to normal working order

Thanks
Mealsonreels :)

System has to be disarmed to Program.
With the Trouble Light on, Press *2, some lights or numbers will show, what are they?
If Phone Company disconnected your phone lines, It will show failure to communicate.
Phone companies are Notorious for disrupting Security.
They should have went to the RJ-31X Jack at the Panel and replaced it.
Or jumped out till an alarm tech could get there.
Is this Still Monitored?
If not, the system can be reset to default and reprogrammed with a new code.