Welcome to YorkieTalk! It sounds like you have received some great advice
I have two yorkies, and my male was 2 when I brought home my female. I always made sure to make sure he got everything first; food, treats, love, attention, etc. He still gets everything first and I have never seen any jealousy from him. He is the leader, but they are both loved equally. Sometimes I take him on errands alone so he can get some mommy time, but most of the time they are together. They are truly bonded and I know he would not want to go back to being an only pet
Give it some time. Make sure he knows you haven't forgotten him... and it will get better!