Keep in mind that the First Amendment says, "Congress shall make no law respecting an establishment of religion, nor prohibiting the free exercise thereof." The federal government cannot tell anyone what is or is not a religion, nor what is or is not a religious belief. No authority at all.

States have the same prohibition via the 14th Amendment and the state constitutions.

Private companies are following a federal government agency's (CDC's) "guideline" which is NOT a law, and are doing so fraudulently, since the guideline has no scientific basis behind it.

I might consider something like:

"My religious beliefs are my own, and nobody can claim otherwise. I believe strongly that nobody may bear false witness (i.e. lie), and I believe I am obligated to expose those who do. It is a violation of my religious belief to falsely claim that I must wear a face mask for a purpose that has no truth behind it (i.e. it is a lie), and that I have an obligation to expose those who do promote such lies. I believe in the Book of Genesis which says that God created the Earth and the air perfectly, as is."

If they do not accept your "claim," you then at least have a factual basis for a lawsuit against them, because they are basing their policy on fraud (no scientific proof that wearing a face mask helps anyone, and plenty of evidence it harms the wearer).

As far as not having enough room, if it is paper, write "See attached" and put it on a separate page. If it is electronic, state "This electronic format does not allow room to express my religious beliefs, so I will need an alternate method to do so."