Fresh water tank drips that slow overnight are usually near the tank top - check fill hose, vent, and overflow connections. Inspect accessible areas before dropping the underbelly.
Black tank flush not accepting water usually means stuck check valve or debris in the spray nozzle. Try direct water connection without regulator, or clear valve with compressed air.
Storage temp spec may be more lenient than charging temp - verify with your battery docs. Most LiFePO4 stores fine below zero. Options are indoor storage at 50% SOC or leaving in RV with heating pad. Main concern is charging temp not storage.
Montana 3793RD black tank valve is at tank outlet near dump connection. Access through underbelly panels. On 2023 unit, likely warranty covered - contact dealer before extensive DIY repair.