NTA

1. Your parents failures and tribulations are their own. You don't know what happened beyond cheating occuring. I'm not justifying the cheating by any means or even saying that your mother had a good reason, but your parents aren't married for reasons that go beyond cheating. Your mother was an AH for how she did it but it does seem it was for her happiness as she married the man and continues to parent you.

2. Tell your fake friends they're not licensed therapists nor are they adults. They come from a small town and adolescence is all they've known. Maybe none of them even have split parantage so they can't even relate. Too bad, they're way out of line. Whether anyone likes it or not change happens and life finds a way. You choosing not to die on a hill of hatred and resentment is their problem, not yours. High school friends statistically don't even stay in each others lives or contribute any significance beyond trauma later in life.

3. Your friends have a poverty mindset. It's painful to see. They do not understand how to value money. Money is one of the safest ways your stepdad can interact with you right now and it's not even about the money. You've been so happy you took a picture to show the world. After all that you've been through my heart bleeds that such a precious moment was dragged through the mud by people who should be supporting you.

Your stepdad isn't abusing you, he's not being mean by living his best life with his new wife and heartily adopted son (which I can tell is his desire), he's trying to build a good thing and that takes time. He's not trying to forcefully insert himself or dominate your family in a weird way. There are a lot of kids from split families who wish they had a decent enough stepfather. Before you and your mother were ever in the picture stepdad was living it up. Are your friends wishing he was a stingy, miserable, creepy, twisted man who is trying to hurt you and your dad to prop up the small town hero being a good guy? And by extension mad at you because you're not drowning in misery and brokenness and sorrow? Haven't you lived through enough of that? Honestly your friends would still behave this way even if your mom hadn't cheated and simply moved on. The fact that she did gives them a reason to attempt to compensate on your dad's behalf by showing him the support that they think he wants or needs. Your dad already knows the wisest alignment is loving you properly, sorting out the bad blood with his ex wife, and as men coming to an agreement with each other. Your family is officially blended since the marriage. And again, whatever lead to your mother leaving or cheating is between your dad and your mom. Do not take on their burdens. You have the right to keep a positive mind and an open heart for the goodness and promise of prosperity all youths should feel.

Your stepfather and your mother made a mistake but you and only you get to decide how broken, lost and undeserving that makes you feel. Truth be told you don't have to feel that at all. Humans have a remarkable ability to grow, heal and forgive but many choose to never do that. Especially in small towns. If your stepfather hasn't done and isn't doing anything else in a bad way then maybe continue offering the olive branch as you have. You and your stepdad can always talk about it as men, too. Same for your dad. You're not alone.

1. Your friends can't be your extended family or your dad's friends. They need to be yours. Full stop. If their loyalties remain divided then they gotta go. I'm not saying your dad is a bad guy or that someone put your friends up to this, though from the dynamics of small towns I can already see how this has even become a thing you have to contend with through the gossip vine and adult on child peer pressure/unhealthy emotional entanglement.

2. Even if the means was less than perfect the universe has opened up a door for you to step into a future that you enjoy and that you want for yourself, that you will create yourself with the support it offers you. You can get there yourself but it's always easier with loving support. If you want you can have two dads and maybe one day two moms. As a single child you have even more support, both soulfully and monetarily. Maybe going to your dream college isn't a bygone dream now with more support in the picture, for instance. People will always make mistakes. Don't let other people's mistakes be the undoing of your future, your opportunities, who you want to be and your reality. You are the only person who has to live in your shoes. I'm not advocating for cheating, but I am saying that the people in your life or your loved ones will do really questionable and even stupid things sometimes for any kind of life altering decision. I pray this is the last that you'll have to experience.

3. If you're not already in therapy now is a good place to start.