I will just point out that the Bible does not teach us to choose our behavior based on whether it furthers our chances to get into heaven, though people have continually attached this concept to Christianity over and over again. Admittedly, some of the language Jesus used might lead to this conclusion at a cursory glance, but it doesn't take deep diving to realize his goal was to convict of sin rather than prescribe a recipe for entry into heaven.

In fact, your goal of living as ethically as possible because it's the right thing to do is completely consistent with the Christianity I believe in; the only difference is the idea of the necessity of salvation and how you determine what it means to live ethically. But insofar as gaining entry into heaven, at least according to the Bible, if you are making so-called ethical choices to gain heaven, you're doing it wrong.

The reason I go to church and participate in Christian activities is because I believe it pleases God and brings me closer to Him (which I realize you stated is not a reason for you to change your behavior); for me, closeness with God is a reward in and of itself. I can tell you that the best moments of my life are Tuesday evenings and Sunday mornings when I participate in corporate worship of my Creator and Savior. Heaven is more of the reward I receive now in this broken world, but made perfect.