You probably are not seeing things straight. As you yourself said, you get annoyed for nothing at times. You also then verbally abuse your partner. It may be that his friends and family see that and feel protective of him.
Further, your partner is correct about his children. They are children and much less likely to hide their feelings than adults. He introduced you to them way too early. They are reacting only like children of divorce often do. Most kids want their parents to get back together. When a parent brings a new partner into the situation, they understand that reuniting the original family is less and less likely. Of course they react.
It’s too easy to write off others’ opinions as “jealousy.” That makes the situation totally their problem. It’s not. You have some serious anger issues that may be grounded in insecurities and anxiety. No one can fix that except you.
If you want to save this relationship, I suggest you get into some therapy right away. At 33 years old, it’s past time for you to develop a more complicated and compassionate view of other people — especially children. Whether or not you are able to learn quickly enough to keep this relationship, it’s important to do it so you can be part of any healthy relationship.
I wish you well.