Yes, I can think of situations where aiming to please another person could be sinful — but that's if what you're doing is sinful. But I don't know why it would be a "sinful intention" in itself to do something to please another person. Don't children do things all the time to please their parents? Or students to please their teachers? Are such actions automatically sinful because they're not done directly for "God's good pleasure"?
Yes. By walking in the Spirit, we bear the fruits of the Spirit and avoid falling into sin. But is intentionally avoiding the lusts of the flesh, the same thing as engaging in them, just because we're not actually walking in the Spirit?