None of what you said is true.

> the federal Gun Control Act of 1968, which gives you the right to manufacture a fire arm

There has been a right to manufacture firearms since before the Revolutionary War, and which has remained a right continually since.

> it must be for personal use

Not necessarily; though you can't conduct business without a federal license, you can, for example, manufacture a firearm to be given as a gift.

> cannot be transferred

See above.

>must have a serial number

Not only is that not true, a federal judge struck down the prohibition on defacing serial numbers in United States v. Randy Price (2022):

https://storage.courtlistener.com/recap/gov.uscourts.wvsd.23...