Food cost is typically thought of around 30% but that is at the end of the day after waste, trimming, theft, whatever. So you begin working towards a 22% food cost goal and keep tight track on the rest and hopefully you end up less or far less than 30%. There are plenty of threads here for you to find quite an education on how to achieve this.
When planning weddings and events, keep notes on what the brides request for food and what they finally agree on so you can assess what you might offer in future once you work out purveyors, availability, costs and the like. Whatever you do, keep it an honest effort and a quality experience. Word will spread for better or worse about their experience with you so I'd expect bookings to increase as the guests have quality experiences with you and talk it up.
You've seen the movie "The Big Lebowski"? The dude abides, as he mentions frequently. You obviously have to do some abiding too apparently.
Given that you like the job and will do it even within the parameters you have, sit down and think about where you would like the operation to go and then work out how you might get there. ( And before I forget to mention, work out an equitable pay arrangement with the owner based on increased business) Don't wait for the chef to screw you over again. Search out some local talent on your own. When the time comes, the owner might just ask "Well, do you have any one in mind?"
And you can have a ready answer. The same with waitstaff, bartenders, etc. Start building your own list of potential employees. Do the same with purveyors, repair people,etc.
How many local groups can you market the operation to? Just weddings or could you get members of the general public to hold events there? Can you create events for anyone?
It sounds like the property is just sitting there and the owner would like to see some revenue but isn't willing to commit to hiring a large staff until there's an actual customer base. If that's not correct, let me know. But assuming it is, I would start thinking as if this were my own business. You have a paid job and a ready property, all you have to do is create the business.
If you are able to do this, would the owner be willing to relinquish more authority, once he sees you are serious about running the place?
Much of course depends on the owner and his motivations. But if you can have a good relationship with him and he's agreeable, I'd look at myself as an owner of an event business and begin keeping records accordingly.