WC (Word Clock) is not an option here, the devices do not support it, so the clock synchronization between BBF#1 and BBF#2 has to be done via digital link, in this case ADAT.

BBF#1 = clock master. In the RME driver settings: set clock source to “internal”.
BBF#2 = clock slave. In the RME driver settings: set clock source to “ADAT” (sometimes also called “optical”).

You need two TOSLINK cables:
1. For sending the clock from the master to the slave:   BBF#1--ADAT OUT------ADAT IN--BBF#2
2. to route the analog channels from BBF#2 to BBF#1:  BBF#2--ADAT OUT------ADAT IN--BBF#1.

According to standards, cable lengths of up to 10 m are allowed, but usually 15 m will also work flawlessly. I have had good experiences with TOSLINK cables from Mutec. Do not use TOSLINK cables with too thick sheathing (e.g., Sommer Cable), then the cables are too stiff and do not lay properly.

Important: make sure that you use the same ASIO buffer size for both devices in the RME Driver Settings to avoid a time offset of the audio channels.

Both devices have their own TotalMix FX instance. TM FX routing only works within one instance.

Therefore, it is best to route the 4 analog channels (Mic1+2, Analog 3+4) from BBF#2 to BBF#1 via ADAT.
For this, you need the 2nd ADAT connection, as already mentioned.

You can easily configure the routing for this in the TM FX instance for the BBF#2, best in submix mode. For this, you click the HW outputs ADAT 1+2 in the lowest row and pull the faders of the HW input AN1+2 IN up to 0dB. Do the same for ADAT3+4 OUT and AN3+4 IN.
If you have audio on the analog channels, then you should see audio arriving at the HW input ADAT 1…4 in the TM FX instance of BBF#1.

Now you can
— record these 4 analog inputs of the BBF#2 via the HW inputs ADAT1…4 IN of the BBF#1 and
— also use those channels for submixes at the BBF#1 for monitoring purposes

This saves latency that you would have when routing everything through the DAW via USB, which would have been the other (worse) alternative, as you have then always the complete RTL (round trip latency) in the signal path.
And this RTL grows if larger ASIO buffer sizes are needed in certain situations.

                                                         PC
                                                         |  | 2x USB cable
   +-----------------------------------------+ +-------------------------------------------------+
    |                                                                                                                      |
BBF#1---ADAT OUT-----------------TOSLINK cable#1------->-------------ADAT IN----BBF#2
                              (transport of clock signal+audio, if needed)
BBF#1---ADAT IN--------<----------TOSLINK cable#2---------------------ADAT OUT--BBF#2
                                           (transport of the 4 analog channel)

Thanks and have fun

A follow up!  After using Ramses advice above.....

The only way I could get my DAW to recognize all 4 channels(2 from each babyface), was to disconnect babyface #2 by removing its USB.  I then added both channels from babyface #1, then reconnected the usb on babyface #2.  After that, I was able to add both analog inputs from babyface #2 into my DAW.  My power adapter was of no help whatsoever.

Hello again Ramses!  I have finally gotten my 2 Babyface chain stable!  The key, was indeed, to make sure I was in PC mode on each device.  There was some confusion trying to figure out the USB controller issue as well, however I found what I needed in the manual chapter 26.3(there is no 28.3!).

Thanks again

There is no 26.3. Did you read the current manual v 1.5 from the web?

Misunderstanding from my side, I thought you have Babyface Pro or Pro FS, but actually, you have a Babyface (1st gen).
Therefore, there was a mismatch in manual chapters in communication, but you found the right chapter

Manual fixes and additions you will only find when looking to the latest manual from web.
Here is the link to the latest manual for your Babyface (1st gen) from March 2016, v2.3.
Chapter about USB audio is 26.3 as you found yourself:

https://www.rme-audio.de/downloads/bface_d.pdf
https://www.rme-audio.de/downloads/bface_e.pdf