Apple has certain connection parameters that must be all met in order to properly function. You can find them in the Bluetooth Guidelines:
https://developer.apple.com/hardwaredrivers/BluetoothDesignGuidelines.pdf
From the looks of your settings, you set your default timeout too high. iOS can only support up to a 6 second timeout. Also, your Interval Max is very close to breaking another connection parameter (Interval Max * (Slave Latency + 1) <= 2 seconds). Drop the max interval down by a bit.
Hope that helps.