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 would be super important for them too. Cannons of all flavors aim with dex due to being ranged weapons.