Are you connecting the 655 as a wired ap using the LAN port and NOT the WAN port? using the 192.168.0.50 should work as I've done this many times however I don't use the larger DHCP pool size like you do.
How many devices do you have and actually have online at one time? Id base your DHCP pool range on how many devices you have that need to be managed by the main host router like PCs and Phones and game consoles. Other devices like printers, NAS and wired APs don't need to be managed with the main host router as they usually don't need any QOS management since they are mainly pass thru for the APs, printers that don't need any internet or do much, and NAS is mainly a LAN side device that LAN side devices mostly need the bandwidth that doesn't effect the WAN side.
I set up all my AP, NAS, printers and 2ndary devices like this in the .30-.60 range as static IP addresses ON the devices. I use the .100-.200 range was my primary DHCP address pool for all other PCs, phones and game consoles. I only have about 20 devices. I could set the pool bigger (.80-.254) if I need however default is good enough.