Looks as good as most of what I've seen. Good job.
I think another fundamental problem is that it isn't clear what people want out of a ship system for a D&D or similar game. Even if the entire campaign is about being on ships, and maybe the ship is the party's #1 focus and valued possession, the dominant unit of focus for each player is likely to be their character. So you probably want your character to be a major contributor to success or failure in any ship-based endeavor (combat or otherwise). You may fee unhappy about the ship sinking out from under you and your character dying (as would make sense in a naval wargame, where your ships are your primary units of focus)-- even if it is still your character's actions or rolls or the like which determine when that happens. Most of all, I don't know if everyone is on the same page as to what ships should be doing -- should ship combat be the biggest factor, or are they mostly means of transport and that the focus? Should it be ships trying to sink other ships like age-of-sail warfare might focus upon, or are they mostly for getting the PCs, sailors, monsters, etc. to each other (boarding or ship as battlemap) with only some ballista and such as armaments? Beyond that, what are you even trying to do with a ship? Does having a larger hold for more supplies, treasure, or trading goods sound like a perk or not (given how desperate the thought on the resources/survival aspect of D&D, what good money has after a certain point, and whether anyone wants to play as merchants and tradespersons; it's hard for there to be a unifying vision for doing so but-in-a-boat).