Yes, there is a $20 fee when eating in one of the alternative restaurants, including Johnny Rockets.
In the alternative restaurant, tipping is already included in that fee, from what I've heard.
I don't know if the cabin on the left side will obstruct the view. It seems OK at the deck plan.
I guess you just gotta wait and see. But it's a Balcony anyway =D
And as far as I know, you are not allowed to bring any alcohol on/of the ship. Not food either, but they didn't say anything when I took a bottle of water through security.
The balcony tables are not huge. More space to eat if you just sit on the table, and placing ur food in your chair =D
I'm sure you will have a great trip, and don't bother about your stateroom view!