Reasonable ruling?

This is probably the best thing you can do for all things. Half the time I resolve issues like this by outlining the plan with the SG and we come to an understanding. I don't like to surprise an SG with something, and as an SG, I don't like being surprised by a player, especially when there are vastly different expectations of what the results should be.

BP are ongoing, but income is a boon or hook.
of course this also depends on whether you use the charts for complex wealth management- simply giving a bonus each year equal to the magnitude of the spell for reasonable use on the income growth chart would be the way I would probably go...

Income other than the typical source is a boon or a hook. The baseline is that every covenant has a typical income source.

ish
covenants p.57 has an income modification chart, which can lead over time for one source of income to be 'modified' into a different level source- personally if it happens this slowly I would not look for a balancing hook for the resulting effective boon. Of course I also house rule that for sources of income tied closely enough to the covenant that covenfolk reaction modifier is added to the roll as well (happy covenfolk are productive covenfolk)

If it happens over time and during play, boons and hooks need not balance.

I'm sorry, but how did your troupe arrive at 380bp for... essentially anything?
That's enough to (alone) have you classified as a Medium covenant, according to the table on p. 71 of the core book, including labs, library, vis sources and everything else?

It sounds like he's talking about inhabitant points? If the buildings can hold 380 points of people you would still need to maintain them.

This shouldn´t be needed should it?

Sounds much more reasonable.

Not necessarily. The ReTe specialist creating a defensible castle could simply have the SG use "antagonists" that ignores normal fortifications of the physical kind.
Or players might be reminded of WHY there were no fortifications, while the brand new shiny castle slowly sinks into the mud. :mrgreen:

I think you meant antagonistic... Anachronistic would be having a digital watch in the 19th century.

Look Fae are just bad at keeping time. Sometimes they're early. Sometimes they're late. And time is really fuzzy in Arcadia on top of that. So occasionally they aren't dressed in time appropriate costumes.

and while having a digital watch is one form of anachronism, so is having a Colt .45

Ah, Colt .45, the drink of fond memory, or more likely, no memories at all....

Build Points are definitely not how I personally would handle this. I would say that it was an increase in the value of an Agriculture income source that relies on cattle. Covenants has more info on this. With that increased income, you should be able to expand your grog force if you so choose - finding exceptional grogs requires stories, but if you want a force of crossbowmen, just find any mercenaries in the area and offer 'em some money and steak dinners.

Also, ask your storyguide what your Tribunal's rules are like when it comes to creating wealth by magic. You may have created a story hook for yourself if the local rules on wealth creation are particularly strict and you try to sell all that beef you're maturing. You also risk causing inflation if you monetize your herd.