Play the character you want. If you do choose to go cleric with an emphasis on war here's what you need to know:
You can choose the Sovereign Host which consists of the most common deities of Khorvaire. Like the Greek or Roman pantheon the religious honor all the gods, but offer prayers to individual ones for need that are within their domains. Clerics of the Host take the longsword as a martial weapon and any two domains.
Dol Dorn - God of Strength at Arms
The chaotic good deity of war, Dol Dorn appears as a paragon of physical perfection who promotes bodily strength as well as martial training. Most often depicted as a heavily muscled human, sometimes as a dwarf or a half orc, and occasionally as a silver dragon, he is said to be the brother of Dol Arrah (god of Honor and Sacrifice) and the Mockery (deity of treachery over honor). Associated with the domains of Chaos, Good, Strength, and War, he favors the longsword.
There is a monotheistic evangelist religion known as the Silver Flame. Something like the Catholic Church post Spanish Inquisition- Lawful Good. They nearly exterminated lycanthropes in Khorvaire and persecuted many other elements that they deemed evil. Church domains are Exorcism, Good, Law, and Protection. Their weapon is the longbow. There is a rustic chapel in Falcon's Hollow supported by some, despised by others. Tensions run high between congregations, often resulting in less-than-holy brawls on the muddy thoroughfares of Worship Way.
Mockery is an evil god, but since it sounds like you are following his path and this is a short run game...
The Mockery is a neutral evil deity of treachery over honor who betrayed his siblings, Dol Arrah and Dol Dorn, and was subsequently flayed and banished from the Sovereign Host. A skilled warrior, he claims evil fighters, rogues, monks, and assassins among his followers. he is portrayed as a ghastly human warrior with the skin stripped from his body, cloaked in the skins of his enemies, and sometimes as a half-fiend red dragon. He is associated with the domains of Destruction, Evil, Trickery, and War.
Also in Eberron the gods are more removed. Your alignment can stray from the one step from your deity standard. I take it that a cleric must have been in step with the deity originally, but doesn't have to remain so. I mention this because your character sounds CN and I would accept that as workable. Bear in mind that the Mockery is a vile god if you take that path and you won't get any love flashing that holy symbol around. But since Falcon's Hollow specifically mentions unacceptable religions choosing to hide out there and it's possible that you are redeeming yourself from some darker moments in the war (making you a compatible PC now) I would be ok with it.