So when you, in your own words, agreed that we would treat each others kids like our own," you were just lying. You meant that he should treat your kids as his own, but you would treat his kids like they're not your own.

The step-parenting arrangements that I've seen that have worked are ones where the parents treat all of the kids equally. You are not treating the kids equally, you are favoring your bio kids, contrary to what you had promised to do. You've lied and you've acted in a way that can only be divisive in your marriage, and you are teaching your kids a bad lesson about selfishness and who you love and who you don't love, and who gets favoritism and who doesn't. No amount of money can make up for your bad parental example in this regard. You've divided your family into 2 groups, rather than into one united family unit. You don't consider his bio kids to be your kids, you have said so over and over again in your message (e.g. "I really just want the best for MY kids" and "I want to do more for MY kids after that" and "I want to do the same for MY kids." and "I just want to help MY kids."). The healthy, successful blended families I know don't talk in these terms. They talk about "our kids" and when they say "my kids" they mean bio and step kids. So your own words just dig you into a hole further regarding how much you are breaking the rule of how you stated you were going to treat your children when you got married. And your pointing out the things that you do do for your step-kids doesn't go one iota towards defending you for what is clearly your unequal treatment in a situation where you had promised equal treatment. Equal is equal. What you are doing is not equal, no matter how many times you take them to an amusement park. I get it--you'll always love your bio children more than your step-children. That's OK--no one can police how you feel. But how you act is something that is under your own control. Even if you can't feel about them equally, you can treat them equally. You are the only mother your step-children have, and you are showing them again and again that they are less than, that your love is conditional and limited. And the kids know it. And your bio kids will respect you less knowing you're mistreating their siblings. And unless you're a huge hypocrite with a double standard, this also means you're OK with your husband treating your bio kids like they're less than, that his love is limited, that the person they regard as a father doesn't see them as his real kids. This is a cancer that will gnaw at your marriage and at your children's family and formative years. You are in complete denial if you think you have "absolutely no major issues in your marriage," when you so clearly have a major issue in your unequal treatment of your children. You need to fully commit to your marriage and to this as your family, not some as family, some as not-quite-family.