Can I somehow route FxA and FxB to different stereo ADAT outputs.
Sorry, no. While the Eclipse has two internal stereo effects, it is essentially a two channel box, so you only get one stereo output.
This is why on UM p.27, the ADAT options are:
Thru The selected ADAT channel will carry the same signal that the corresponding ADAT input carried.
Mute The selected ADAT channel will carry silence.
Ch 1 The selected ADAT channel will carry the Eclipse’s channel 1 output.
Ch 2 The selected ADAT channel will carry the Eclipse’s channel 2 output.