Really cool shape ! What's going on in the middle of the world ? The round ocean I mean, it seems to be a special place...
And how would you describe the impenetrable mountains surrounding your world ? I Mean.. How impenetrable is it ? Like a 10 km height wall of rock ? Or is it the terrible nature and monsters living in there ? How do you expain that noone can go there ? I'm really interested in your answer, because as a game master I always try to let some possibilities if players really want to try something. I also guess some places in my maps that are critically hazardous, but if you really want to go there you can try you know :p
If you allow me, the only thing I would advice is to set some other little isles far away the shores, or actually to move some of the already set isles from the shores to the sea (some of them are a bit too aligned, so moving some would probably solve both the lack in the sea and the concentration on the shores). For now, except for big continental parts, there's no isle in your oceans (except in the east south). But it's only my opinion, you may disagree
Well started ! Looking forward to see the development