My 32-year-old co-founder has a brain tumor 13 years ago
I see myself in his post. I was diagnosed in my 20s. I have been through a very similar experience.
If the blog author reads this: eat. Then eat some more. I cannot stress this enough. Having some disposable energy (fat) stored on you makes facing a major illness _less hard_. Myself, I lost 15kg going through chemo and radiation therapy. You are already skinny...
While you eat, spend quality time with your loved ones. You will never regret it. You have a beautiful daughter and a lovely family.
In my experience, the two most useful things during treatment are emotional and physical support from your family and friends, and therapy with a psychologist.
Be strong and God be with you.