Small Business Owner - 64 year old employee threatening to leave and take clients - is he a fiduciary?

3 years ago I purchased a financial planning business in Ontario with 6 employees. 1 of my employees is 64 years old and has been with the company for 30 years in benefits sales and is considered a broker. This benefits broker works without oversight/independently and is responsible for about 1/4 of my gross revenue.

Our relationship is deteriorating and he's threatening to leave because he feels he deserves more pay. As such he believes he has the right to take the clients he's brought on with him. I say they belong to me and my business.

I am in a situation where I cannot afford to pay my employee more (nor is he deserving of more pay), cannot afford to pay him 1,5x salary as severance, and I do not have a relationship with the clients he wants to take. I am at his mercy.

This employee is not under any contract and doesn't have a non-solicitation agreement.

I have read that said employee could be considered a fiduciary to my business. I have spoken to two lawyers and each has given me a different opinion. alas ... Im here now trying to figure out what to do,

thanks in advance for your input