LA Caelum vs. Ermor

[Stossel]

I'm playing LA Caelum on Glory of the Gods (the 480 province version). My first neighbor is Ermor. I've always had problems dealing with ermor in Dom2, and I still can't manage to deal with them now.

Here's my situation. I'm two provinces away from his capitol. I've got a chokepoint holding against him with earthbounds and archers, along with 3 elders and a caretaker. I can hold out against him indefinitely (ferrying troops back and forth every so often) but on the times I've tried to push him I lose horribly.

Now I've got pangaea coming in from the opposite direction. Any tips on dealing with Ermor?