No. Even if a Firefox webview existed, it woul'd not use the extensions from your main browser.
An adblock option is available from the native alpha settings if you're interested.
This is unrelated. You want to familiarize yourself with the concept of OS integrity and how it is different from data encryption. You can have a passphrase that encrypts your data alongside having access to these hardware features.
It has very minimal code and its implemented in a robust manner. Unlike UEFI and the desktop implementation of secure boot, it does work well and it has not yet been exploited on pixels. Its way better to have any kind of OS integrity check than none.
The fact that youre illiterate and you're hallucinating stuff i never said, is sad.
I will address your concern however.
If you think that they are actually not encrypting the message content, then you're a conspiracy theorist. They have thousands of other ways to track the user and give metadata to law enforcement. There is no need for them to lie about protecting the messages, as none of the regular users care about that. They had more than enough users of Messenger even before it was E2EE.
If you're an adult, and you're interested in children's romance thats the same issue.
In fact, all content directed towards older audences featuring this kind of stuff, is directed to, and made by pedos.
Because you make it that. Its political for you but for me, no.