So there's actually a person playing on an even smaller screen than me! I think your issues with the game window size and the small font are related to that. Having a laptop myself (though with this game the size is alright for me) I can only suggest you try F11 to fullscreen the browser, if you don't already. Removing the header and task bar from view increases the size a lot because they improve the more limiting vertical size.
For the 'not enough going on': yes, I'm feeling the same, especially with all of those gems feeling unrewarding, because there's nothing to do with them. But I think the game is just not finished on these things. It also looks as if there's room for more buildings to the right side.