Seems your friend is one more person who pushes you away? Have you considered that you may be wanting to help and keep on pushing after they ask you to back off? I suggest you just let them live life as they want instead of insisting they accept your help.
Your sister in law asked you to stop helping her mother with the porch, yet you insisted that you do what you want.
Same with your mother in law. She is able to take care of herself. When you hover you are telling her she isn't able to care for herself. Do you not realize that when you insist, you're telling her she's helpless. You're making her feel worse.
Now your widowed friend. He is telling you he doesn't want your help. Yet you want to find a way to make him accept your help. Why can't you let others decide what is best for them?
Perhaps helping makes you feel good about yourself. Now accept that they want to do what makes them feel good about themselves. I suggest you only offer help when someone asks for your help.
Your friend has told you he doesn't want to talk about himself and his wife's death. He has the right to grieve any way he chooses. When you push yourself on others, you're disrespecting them and their ability to make decisions for themselves.
To your question "what did you do?" You have not allowed him to grieve as he wants. When you insist he talk with you and continue to socialize with you, you are telling him what you want is more important than what he wants. Can you accept that what he tells you is the only way to help him. Acceptance means you'll let him grieve the way he's chosen. That you will stop pushing him to do what you want. Let him be in charge of how he grieves.
This means you don't call him, don't invite him to do things with you. Let him come to you when he wants. Honor his decisions. Honor yourself by accepting his choice.
Seems like you like to help. I suggest volunteering where people want your help. Work at a food bank. Serve food at a shelter. There are many organizations who would like your help. Choose one in which you can agree to follow the coordinator's lead. Learn that you are valuable when letting someone else tells you how you can help.