Hello, Mike--
That is a great rundown of the human condition. Regular people become heroes, then other regular people expect the hero to not be regular.
Lemme see if I can answer your questions.
1. How did Lindy come to scroll through Tyler's phone? I don't know the details, but I do know that she was invading Tyler's privacy by going through his phone. That definitely wasn't cool of her.
2. Did they have an agreement of mutual faithfulness, or was she making an assumption? They had an agreement of mutual faithfulness.
3. Does he deserve forgiveness? To me, yes.
4. Does he do good work in law enforcement? Yes, as does Lindy. I may have forgotten to mention that she, too, was a law enforcement officer.
5. What is his side of the story? He cheated on Lindy with multiple others.
Your questions have sparked me to think of some questions as well.
1. What is the worst harm that could come from Tyler cheating on Lindy? I'm thinking...he could have given her some diseases, some of which might be 'merely' painful for the rest of her life, some life-ending.
2. If Tyler had given Lindy HIV that he contracted from cheating on her, without her knowing that he was no longer monogamous, what do you think should be the consequence for Tyler? If this were a crime--endangering the life of others--what do you think the sentence should be? Should he have to pay for her medical treatment for the rest of her life?
3. What is the worst harm that could come from Lindy's invasion of Tyler's privacy? I mean, assuming she's not stealing his bank account numbers. The only thing I can think of is that she finds out he's cheating the harm is that they both lose their relationship, and she has to live in a city where she moved to be with him by herself. But maybe there are some other worse harms I'm not thinking of.
4. What do you think should be the consequence for Lindy's invasion of Tyler's privacy?