All of your points are valid.

I have this to add:

This portueguese spy, acting alone. How much gold did he need to get
there? And, notice he got taken out, anyway, when he was discovered.

I feel that to find out about the wedding is no problem. However, this
seems to me that this could (or should be) an action for a lieutenant
NPC, and not the province of the spy, who finds out how many gold bars
are stashed below thae castle.

Also, you claim that espionage is somehow different "Today."

I'm just tryibng to show an analogy, such as how much info can an
untrained person get by showing up in Canada at a base or something with
a lot of gold, trying to bribe/buy their way in. Maybe sucessful, but I
think in the long run, probably not.

What I'm saying is, the PRINCIPLES of spying are the same.

Machiavelli's "The Prince" bears this out.

Because this is the 20th century doesn't change the way spying is done,
it only changes the information that is gained (Maybe with help from
satellites, etc.) That's my point. People getting other people to turn
against their country, for money, or whatever. THIS is the basic craft
of the spy, and hasn't changed since the days of Caesar.

- - James H. Jenkins