Richy,
From all of this it does seem to the outsider that you don't have a clear idea on how your business is trading. Like colley said, you really need to sit down and work out your true figures.
Before you can estimate what your guy is worth to you, you need to have a costing spreadsheet which outlines all overheads (include 18K wage) and all income, this will allow you to get an idea of your profit.
You also need to be clear what you want to achieve and make this realistic, focus on what business you currently have and how this can be run efficiently and profitable. You really need to stop with the million different ideas you have and concentrate all of your thinking time in to this. Then when you are happy the business model is working and you are making profit with good staff and low levels of staff turnover, you can mess about with other ideas.
All of the time spent on this post alone by yourself could have been spent by you sitting down and getting a real understanding of your business. You need a business plan, I would suggest that you get an outside eye to look in at your business and help you to see things clearer. Sometimes there is nothing better than an outsiders view.
I would suggest you contact your local business link or similar and explain you need a business mentor to help you.
Hope this helps