nevermind verifying the important claims like "How do we know theres a fixed amount of bitcoin?" or "where does the bitcoin come from that is awarded to miners?" and "How do I know my access to my wallet can't just be shut off?"

These things are easily verifiable without having to directly access the code of Bitcoin. Anyone can download the software and run it on their computer, which downloads the entire blockchain and verifies every single transaction ever made. All anyone needs to do is visit a block explorer, which is a website that serves a searchable interface for the blockchain so anyone can verify any transaction. The only "trust" that is needed is that the miners will continue to be self-interested in earning more Bitcoin so they will continue securing the data held on the Blockchain. The miner rewards are predetermined for every block so we know exactly how much Bitcoin has been mined by adding it all up. The rewards are cut in half every four years until it reaches zero at which point the miners will only be rewarded by transaction fees.