OK so from my understanding, the only inhabited structures planned are the smugglers' den in the ruined castle and the trappers' lodge.
Considering the remoteness of the entirety of Cracklaw, why not have a surviving settlement somewhere? It can be presumed that the Cracklaw people are fiercely territorial, so its not a stretch to imagine a squalid settlement or two hanging on made up of former nobles now poorer than most peasants.
If you've not seen the 1670 mockumentary series on Netflix, I recommend something like the "manor" at Adamczycha, but even poorer. Its pretty much a big peasant cottage but with some nicer trappings.
When it comes to the castle tests I think you should decide at what point the castle was abandoned fully. If it is after 50AC, (250 years ago) imo there could be a pretty stark change to the castle made. Because of Hardy's more exposed location, I think it would be more likely that Celtigar tax collectors were successful there. Because of Jaeharys' Merlon Tax, its likely that the Hardys had to remove the crenelations on their castle in order to pay the tax on their castle. If the castle was inland and cloaked in forest, I'd say it would avoid this treatment regardless of the time of abandonment.
Also, I do think you should think about the idea of having wreckers/ a lighthouse on the point, potentially instead of a castle, would suit very well.
It would be good to lean into the square versus round tower divide that George describes in regards to First Men-Andal building practices. It'd also more closely resemble Dunnotar, which did not have many round components. Dunnotar has the very fun detail of having really strong defences at the gorge that cuts it off from the mainland, which means that despite the dunnotar headland being lower, you still have to ascend 5 metres or more to get to the castle gates. It also has a very open series of buildings behind those initial walls, though not as extreme as similar castles such as Tintagel in Wales. Imo doing something like that would be far more effective than the current wide plain before the walls in the test images which look a lil bit more like a stone version of the Jaromarsburg temple. That's my other main point. Imo, make the land slope down slightly towards the castle, then put the break between the headland and the castle itself like your dunnotar insp.
Additionally there's a really cool easter egg/silly detail you could put in if you wanted to. As the NE tip of Cracklaw, surrounded by Crab themed names, you could make the castle mount actually look like a crab claw a little. Dunnotar already does, from above it has the central < cutaway where a sea cave is forming.
Considering your headcanon, I presume that the wealth to build the castle came from looting other Cracklaw houses and collecting tribute/taxes. That still means you'd need quarries to build the castle. Having a few overgrown quarries could look really cool!
On a more technical note, the gradient in the tests doesn't always seem to follow a solid rule. Sometimes its fieldstone->dark cobble, a lot of the time its fieldstone->river rubble. I'd say either have two patterns with different rules on different structures or apply a rule more thoroughly so it doesn't seem too random and messy.
When it comes to the terrain I'd look at doing a bit of a high blanket bog for that central marsh that will distribute the water to both northern and southern sides of the point. Blanket bog is basically bog on a slope. Considering we now have access to waterlogging, modifiable heights of water, putting vegetation on slabs I'd say there's no excuse not to make a realllly cool wetland landscape at the top of the hill. There are a lot of diagrams out of Ireland on this kind of landform.
I've got a little suggestion about the highpoints where I've included some hypothetical streams (rough locations) as well as a denuded/gnarled tree zone on the peak of the ridgeline and high points of the project which would be a really harsh landscape to match the name of the house.
I didn't see any tests for the Trappers' lodge or the abandoned settlement but presume you'd use the Boggs or Pyne styles of houses. Do you have any tests for what schems you'd use in the forests, or dioramas of what you'll do for the marshes? I'd not recommend the salt marshes of Boggs but instead to do something a bit more like a Fenn or Carr environment with lots of braided streams, tall grasses and ForestAlder shading the upper parts away from the beach. Could even put in a spit or two sealing the marsh into a bit more of a lagoony kind of thing if you have room. Definitely chat with NMF about what to do with the coast lines, they've done an amazing job with the beaches and figuring out Longshore Drift