I would highly recommend talking, in an active listening sense of the word. If you were able to arrange a time to talk about your relationship with your partner and decide beforehand to stick to the "rules" about taking turns talking and listening to each other, that might help a bit with diffusing angry feelings that come up.
Acknowledging anger when it happens is different from acting anger when it happens, by the way. Saying "this makes me feel very angry" is a good thing to communicate to a partner. Giving them the silent treatment or yelling at them is not so good. Believe me, I've done all of the above..
For me, the two pillars of poly are communication and respect. If you don't have either of these for your partner AND for yourself, poly will be incredibly difficult if not impossible.
Try and remember that everyone has needs and emotions that they're scared of communicating for fear of being rejected. Fear is, I find, at the root of most relationship blockages, and if we can find the courage to open up enough to admit our fears to our partners and especially to ourselves, we bridge a huge gap in creating trust and intimacy with our loved ones.
Taking small steps to building trust might involve suggesting a "truce time" where you simply sit together and hold hands and appreciate the other person. After acknowledging you still have this connection, it might be easier to talk about some of the scary, difficult feelings you both have.