To be an access point your configuration seems okay.
However there are many factor concerns the real performance so you should provide more detailed information for us to improve.
The below are some elements I can think of:
1. Interference. You can use a laptop installed with Inssider to detect the wireless environment around the device to see if there many other devices working around.
2. Obstructions are Wi-Fi killers. If there is any obstructions between AP and Clients, the connection becomes unstable that leads to packet loss.
3. Too many client devices or running high traffic on clients result in disconnection issue as well.