Hi,
Regarding your questions,
1. You may want to get in touch with the manufacturer of this device to confirm whether they are rejecting authentication based on the manufacturer and device ID, and whether your device could be added to their list.
2. The Fitness Equipment device profile specifies that on the watch device (display), the ANT-FS channel should remain connected throughout the session. Wording cold be clearer, but essentially, this means that the watch should keep ANT-FS in transport state (infinite link timeout) until it loses the FE-RX channel.
3. FE's are not required to download any files from the watch, but most of them do download the settings file.