Check that the volume adjustments in the DS01 for speaker and microphone are around he centre position.
Then load a default set of tuning parameters into Comfort as I see that you have made some changes
The default tuning parameters should give acceptable performance with the DS01 trimmer adjustments in the centre so start with that.
If you try to imcrease the parameters for the door speaker volume it may cause the Mic gain ie in the other direction to be reduced to compensate
When you say volume at the Door Station is very low, it may be not because of parameters but because of connections - DS01 Speaker to DM02 (SPK - Do Door) or DM02 Voice to Comfort
CAT 5 cable should be no problem
The volume for intercoms cannot be very loud as there will be a problen of howling or positive feedback - this is a common problem for all full duplex intetrcoms
Hence if it is audible ie can hear the voice clearly from the other side then it is working as expected
If the DP to KP is loud and KP to DP is low then yoiu can get louder volume in Kp to DP by reducing DP to KP volume
Change Tuning parameters as follows
Tune parameter 1 DP (EEC) volume for KP to DP Intercom change from 30 to 37
Tune parameter 79 AFE KP Mic gain change from 8 to 10