It looks like your cluster controller is configured for Bisynchronous communications. If this is the case, MacDFT can provide CUT support only over Bisynchronous, so switching the coax CDEV setting to CUT mode should work.
The significance of the "DFT (NON-SNA)" setting is to support non-SNA channel protocols for locally attached controllers such as the old 41D models. Since your 61C is designed for remote connections, it isn't prepared to handle channel protocols, and MacDFT notifies you of the conflict.
If you're not trying to maintain Bisynchronous communications, and SDLC communications are OK, then you will need to check your controller's customization; if it is set for Bisynchronous, you will need to change it to SDLC in order for MacDFT to provide full DFT capabilities. The attach option is configured in customization question 101 on the "Model/Attach" panel of the customization utility (see the 3174 customization manual for further reference).