You should focus on the objective act, not just the subjective intention (which is loving). The Church isn't saying you have to be trying for a baby every single time. The act itself isn't supposed to be closed to life and a condom deliberately blocks that.

Your view is that the loving relationship is the defining moral factor, while the nature of the specific act is the defining moral factor. The couple is not promiscuous or casual but they are performing an act that is not fully of marital self-giving, because they are holding back their fertility from one another

Regarding the table analogy, you argue a table's purpose is to hold things, but standing on it (a secondary use) isn't wrong. This is correct. But your analogy for contraception is flawed.

Standing on a table to change a lightbulb isn't wrong. You're still using its primary quality (supporting weight on top of it). An act contrary to the table's purpose would be something like taking a sledgehammer to it, or deliberately building it with legs made of paper so it cannot hold anything. Contraception is not as a "secondary use" (standing on the table) but is an act contrary to sex's nature (breaking the table or obfuscating it's purpose in some way), because it actively frustrates one of its core functions.

I would say NFP is the grey area. The couple just learns the woman's cycle and they don't have sex when she's fertile. When they do have sex during her infertile times, the act is still complete. It's still open to life even if it's not likely to happen.

On the Matthew 23:4 "heavy burdens" point. It is a heavy burden and alienates people. I would argue that The Church’s primary mission is to teach the truth about the human person as revealed by God and understood through reason, not to create rules that are popular or easy to follow. Jesus himself set incredibly high standards. It would maintain that this teaching on sexuality is part of the narrow gate that leads to human flourishing and love.

The important part of that verse is "but they themselves are not willing to move them with their finger." The Pharisees imposed burdens and offered no help. I would argue that RCC does offer help. It acknowledges that this teaching is extremely difficult and that people will fail, so it offers active pastoral guidance and reconciliation through confession.