I mean, if you have the ability to build a spacecraft and get there, you’ve already overcome far larger barriers. Any physical security on the door is going to be comparatively irrelevant as a barrier.
Locks, like walls and other passive defenses, aren’t designed to stop people. They’re designed to keep basically-honest people honest and slow down the rest to the point where other things, like people, can deal with them.
https://en.wikipedia.org/wiki/Safe#Burglary_ratings
The highest safe rating here against burglary is 30 minutes of resistance against someone equipped with suitable tools (like, cutting torches and such).
If you can get up to the ISS, it’s a pretty safe bet that nobody’s going to show up in 30 minutes to do anything about you entering.
The President can’t amend the Constitution. In fact, the entire federal government’s only role – not talking just the Executive Branch, but also the Legislative and Judicial – is, in one of the two amendment routes, to propose the amendment. In the other, they have no involvement at all. The amending process is really a process done by the states.