You've been given excellent advice, but I'm going to go one step further. Definitely provide your FIL w/your h's telephone number. Once you have met w/your FIL over dinner, you can then assess the situation and provide in your brief text to your h what is going on w/his father. Whatever the two men decide to do about communicating will be up to them. They both will need to set aside their pride if they are going to reconnect. Your h's journey may require that he and his father finally bury the hatchet and begin the healing process.
Do not worry about how your h will react. You are doing the right thing and one day maybe your h will appreciate the gesture.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
