If I share a photo album on Facebook with "custom audience" then will their mutual friends will be able to see those photos?
I want to upload family albums and I want only selected people to see.
If a person in my custom audience comments on a post, can their friends (or our mutual friends) then see the post? (People who aren't in the custom audience.)
No, other people will not be able to see that post.
From What does the "Custom" privacy setting mean?:
When you choose the Custom option in your audience selector, you can share something with specific people, or hide it from specific people. You can also choose to share or hide posts from friend lists if you’ve set them up. Custom also gives you the option to share with groups or networks you belong to.
See this for more details: What audiences can I choose from when I share?
