Have you considered?

If I wanted that I'd just play Divinity 2.

I'm deeply disappointed you didn't take the chance to go with "Ditch the caves, hit the waves!"

Ditch the earth, hit the surf!
- Get out of the tunnel and swab the gunnel!
- Off the turf, in the surf!

I have issue with almost all of your points.

Dex & wisdom would be the important stats for sailors IMO (i am not saying strength and con are useless, but just not as important, they would be 3rd and 4th IMO).
Darkvision wouldn't do a damn thing, its range would barely get off the side of the boat.
Poison resistance is not disease resistance.
Some spoiled food would be poison, but some would also be disease (depends on how it spoiled and the food).
In order for short stature to be relevant to ship design, they would need a completely custom designed ship tailor made for them, which would have benifits but sounds unlikely for what pirates would be sailing. (That being said, a dwarven merchant ship designed speciifcally for their stature would be a massive pain for normal height characters to battle on)
lower speed means they swim slower too which means going overboard is even worse.

EDIT: dwarven submarines!

short stature actually hugely relevant as submarines are notoriously cramped
darkvision means no need for lights in the sub, beneficial for multiple (admittedly somewhat minor) reasons.
honestly no clue what stats would be important for a sub, no argument here
toxic gasses less of a problem thanks to poison resistance
Dont even need to go to the surface, a fully underwater submarine port could be connected to existing dwarven settlements near the ocean with the correct design and planning.
Also benefits from legendary dwarven engineering.

Dex is good, but IMO it's not as vital as Con. Sailors were dying a LOT, and it wasn't from accidents. Con would help a lot with diseases (those were rather common on sailing ships), the exhaustion inherent to working on a sailing ship and the lack of nutritious food. And scorbut, which is a disease, was one of the biggest issues in intercontinental sailing.
Darkvision might not do jack for navigation, but it would be very useful when you need to work day and night and the only available light sources are torches, oil lamps, candles, moonlight and starlight.
The OP never even mentioned pirates.
AFAIK most sailors couldn't swim at all, and when would the lower speed actually be an issue? In most cases, it's all about whether you get exhausted before you're at your destination.
Great point with the submarines, though.
Dex is valuable for tall ships, but steamships and ironclads, str/con is the way to go.
- tall ships are a hate crime to dwarves
- Dex would be super important for them too. Cannons of all flavors aim with dex due to being ranged weapons.
For sure wisdom being the highest priority unless they always sail near the coast, but to be fair you only need 2 people with high wisdom
These are all problems humans already have and try to get around. A few adventurous and entrepreneurial dwarves is all it would take to kick start the golden age dwarven naval empire.
I am looking at this from a fun world building viewpoint and I find this idea exciting.
The height being an issue for other creatures gave me a funny thought. If dwarves didn't build massive structures and instead built for their height, people invading them would have such an issue. You'd have dwarves running through halls chopping at them while they're crawling around or bent down. Invaders wouldn't stand a chance.

Darkvision limited to 60ft. Nighttime navigation was based on stars.

A ship can barely contain enough ale to last a dwarf a month, let alone an entire crew...

below decks in ships were notoriously dark
- That's a feature, not a bug.
- Gay darkroom vibes
Darkvision limited to 60ft. Nighttime navigation was based on stars.
You don't need darkvision to see stars and that would be dim light, so darkvision is a boon
- Then it doesn't help navigation
Tbh, that's a rule that makes sense in context and something where I as a GM would make a house rule.
Even the darkest night at sea is not nearly as dark as the mines, so I'd totally allow for darkvision to be range-less (or long-range) on the sea.
Edit: deleted because I replied to the wrong person

Marcus Miles has entered the chat.

That dude's a beast.

Having lived on a boat for years, I can tell you right now, you show me a body building midget, and I'll show you an amazing marine mechanic.

Splittermond, a German RPG, has a culture of arctic viking dwarves. It's perfect.

I am a dwarf and I'm sailing a ship

Saily saily ship

One of my favorite campaigns I was a tempest cleric dwarf in a sea campaign. She came from a clan of dwarves that would take longboats along river coasts downstream from a mother clan's mountain mining to find pockets of washed down minerals. It was so fun and eventually she started her own seafaring clan the Sundersalt. We were based on an island but controlled a lot of trade in the area with ships modeled after Korean turtle ships

Saily saily ship

The copper dwarves are excellent sailors.

They aren't very buoyant though, are they? What happens when one falls overboard?

You go back and mine another one.

"The Boat Ramp of Durin, Lord of Mooria. Speak, matey, and enter. I, Narvi, made it."

I would say dexterity isn't such a bad stat while moving on the masts or wet planks. and since they can see in the dark too, and further because they are much larger, elves win again -.-

What is this, dwarves for giants? Those fuckers are at least 5m tall, goddamn.

Can dwarves survive such prolonged periods so far removed from rock, stone, and dirt?

Similar to vampires, every dwarven ship has an enormous boulder occupying a conspicuous place in the quarters. Sleeping near this "home stone" is necessary to prevent dwarves from going sea crazy.

My previous character was a Dwarf Marine (barbarian, path of the ancestral guardian). He was wielding an anchor as a 2-handed weapon.

He met his fate killing a sub-boss. (that is: a boss that came from the sea floor, the captain of a submersible galleon)

THANKS I NEEDED THIS

Ah like in Warcraft 2 you can have submarines with dwarves

Craftsmanship is also highly valued on a boat...