That 100 ohm between to terminals provide DC bias to each node. So there is no need. You can put if you want but if there's mismatch between them you'd burn unnecessary power.
No. To make both common mode voltages equal, you would just omit the capacitors. ECL and LVDS I/O standards have different common mode voltage, that's why the capacitors and the bias network are used.Now to make the common mode voltage same of both (LVDS and LVPECL) we are using a resistor divider.