Let's make this simple:
1) 410.9625Mhz is an analog vehicular repeater frequency and always has a tone of 123.0hz on it. If you find you can hear it when you remove the tone, then you've programmed something wrong. There is no point in searching for a NAC code as it's an ANALOG frequency.
2) You need to find the closest tower to Strathroy and program in that site. Judging by the map, it would be London, Ipperwash or Wardsville.
3) As I previously said, the detachment has an antenna on the side of it and a very expensive radio. Just because you can't hear the system, doesn't mean they can't.
Except for making sure you've got the system programmed in correctly and haven't locked out the talkgroups, you'll need to invest in a better system if you want to hear them better.
With the new setup at the detachment, there's no reason to leave the vehicular repeater on anymore while at the detachment. That's why you're probably not hearing that frequency as strong.