1. Is it normal to get hot when charging?
Yes, because of its small size, when fast charging is provided, the IC will gradually become hot, which is normal for the battery pack.
2. What is the real capacity of this battery pack?
It has 5,000mah, but it ends up providing less than 5,000mah of energy to your device. Because it loses energy when it is discharged, this situation is normal for battery pack.