Brandon,
my wife also has brain cancer. there is no easy or simple solutions.
Some advise, be specific with the help you need from people, they offer help but dont know what to do. Tell them what you need. If you need time then tell them I need an afternoon or whatever.
Try a support group for caregivers, mind you i have not done this but it sounds to me like you could benefit from it, you are not alone.
Are you religious or not, for me much of my strength comes from my faith.
lastly, and this might sound harsh, devote yourself fully to her, she is going through an unimaginable journey and only since feb. My wife has glioblastoma for one year now and she is very tough but i have sucked up a lot of fatigue and stress.
You must take care of yourself if you are to be of use to her, be pragmatic and get the help you need, trust me i know what you are going through, its a rollercoaster ride and every day is different but i have learned from the experience so far and from my wife to cherish every day and live as hard as you can, none of us are gaurunteed tomorrow,
let me know your thoughts, Ill keep you and your wife oin my prayers,
Peace, Carl