Randyman's suggestion is the best way to connect, but I just add a few things regarding what you mentioned.
Synchronizing is commonly done via Word Clock (using BNC cable), but also possible via SPDIF or ADAT connection. So, what you heard was right. The thing you need to remember is, there should be always master-slave relation in clock synchronization. That means, when you want to use FF as a master and either of your Focusrite preamps as slaves, then those Focusrite units should receive clock signals via SPDIF or ADAT. But I don't think either of your preamps have SPDIF or ADAT 'inputs', right?
FF UFX can be sync'ed via ADAT, if you use either of your preamps as a master using SPDIF or ADAT. In this case, clock signals are carried on the same cable as the digital audio signals. So, try connecting EITHER of the preamp's digital output (SPDIF of 430 MkII or ADAT of 828), and tell FF UFX to do external clocking (FF UFX is slave then). It should work as long as the clock selection of preamp's AD converter and FF UFX's control panel's clock selection is matched. This is the way two devices are synched without word clock cable. BUT as soon as you connect BOTH clock source (SPDIF AND ADAT), FF UFX will think and be confused, 'which one is my master?", and synchronization doesn't happen. Only one unit should be 'master' and the other two should be slave. If you make FF UFX as master, then your preamps should be slaves, but you need to use word clock cable, because they (preamps) don't have SPDIF or ADAT 'input'. Does this make sense?
The reason Randyman suggested to use 828 as a master is, usually it is the best to use the front end AD converter as a clock source.
As to the termination, you can look up 'digital cable termination BNC' and should be able to find a one. Some units have internal terminator, and I believe FF UFX has internal termination. After all, 828 (Master) WC BNC out -> 430 (Slave) WC BNC in -> 430 WC BNC out (WC daisy chain) -> FF UFX WC BNC in, is the right and the best way (without using terminator plug).
Hope it makes sense.