I'm sorry for your bad experience. Alas, you have plenty of compan

For example, until last year one man owned every McDonald's (nearly 20) in the Reno area. Due to the activities of his office manager (not worth detailing here), he wound up losing every franchise, and his corporation was fragmented. Today he's trying to get a single restaurant up and running.
Yet, you cannot do it all yourself; that's why you hire people. There are controls you can put in place.
One of the most common is .... are you ready for this? .... a generous amount of company-paid vacation, to be taken in one-week increments. Why? Because the temp will likely identify any irregularities during that time. (Uh, Mr. Smith ... I don't understand this ...) Another is to split the activities among several parties.
It's probably worth it to have a CPA set up your bookkeeping system, with some of these controls built in. This ought to free you to do your job, and reduce the things you need to monitor.
Finally, there's a role for prosecution. Having the entire crew send a birthday card to the perp in prison will get the message across!