As a former Marine officer and Vietnam vet,I can tell you that it was the most rewarding period in my life. The Marines that you command will be the best people you have ever met. There were Christian Marines when I was in and I'm sure there still are.
You don't kill for killing's sake. You kill to protect yourself and your fellow Marines.
No matter what MOS you have,as an enlisted you are a rifleman first.
As an officer you are an infantry commander first.
I was an 'AirWinger',A-6 driver. I ended up,by fate ,commanding a rifle company in combat for 47 days. It was the scariest,best time of my life. MY Grunt Marines were the best in the world!
It is a major decision for you. If you pick the Corps,IMO it will be the most rewarding and satisfying in your life.
Always Remember-Your Marines come first before anything else,You included.