There is nothing wrong with "among my friends" (or "amongst my friends"). You do need to add a possessive pronoun before 'dad' though, e.g., "I was the only one to my *my* dad around amongst my friends".

Thank you, Sierra Cleland, Paul and Su. Ki.

Agreed. You have to capitalise 'Mom' and 'Dad' here, because they are proper nouns, the same as people's' names are proper nouns. Using lower case would only be possible if you were using them as common nouns, as in 'my dad'. This is a key distinction. Just as you have to capitalise 'John' but mustn't capitalise 'my brother', you have to capitalise 'Mom' but mustn't capitalise 'my mom'. Capitalisation (or lack thereof) is not an optional nicety. There are rules.

When they are used in place of their name, you do. If he had written 'my mom/my dad' then it would be incorrect to capitalise.

There is nothing wrong. You don't have to capitalize "Mom" and "Dad" but you can.