Hello, and welcome. I am a licensed attorney and happy to assist.
While it definitely sounds like you need new friends, the law is also 100% on your side here. Because the trip was not conditioned on payment and you only offered to throw in money gratuitously, you have no legal obligation to do so. No court would award your "friend" any money. This is not because he was such a jerk on the trip, but because his position is simply not grounded in the law.
As far as his interference with your business, this friend could be liable to you if taken to court. Your causes of action would be defamation, if he is spreading lies about you in a business capacity, or interference with contractual relations if he is interfering with your sales.
With regard to the threats, you could potentially obtain a restraining order against this person if he has made a credible threat to physically harm you. This person also may not realize that threats to obtain money to which a person is not legally entitled can be construed as criminal extortion.
I hope this helps. If you need additional information or clarification, just let me know and I'll continue to provide assistance. If I have addressed your issue and/or pointed you in a positive direction, please let me know that, as well. Also, please remember to leave a positive rating when prompted, as that is the only way attorneys on this site are credited for the help we provide.