I agree with you on abortion, but it's not a function of the federal gov to codify a medical procedure into law, forcing states to allow it.
You say the 2A is murky, but the federal gov authority to regulate marriage is absolute. It's the other way around.
The 2A is not murky, it's very clear. The right to keep and BEAR arms shall not be infringed. So,.if a state say you can't carry a firearm, that would be infringement. That is against the cotus, and against our rights.
You would say that if cotus says gay marriage is the law, that is fine, then you would also have to recognize that if the cotus said carry laws were unconstitutional, that too would be fine...but you won't, will you?