There are a couple of things/approaches:
1. Figure out what slows down the device/app
2. With services, the Map is stored in process globals. As your watchdog doesnt kill the process, just the service, you dont need to write anything to file.
3. If you kill the process (with ExitApplication), you can write out the file in Service_Destroy and read it in Service_Create.
4. I am not sure what you are storing in the map, but i guess it will setup a new connection anyway.
5. Watchdog.Map being 0 is worrying and worth investigating.