However, that being said, it by no means condones homosexual behaviour and still less “gay marriage”.
You might also find it very helpful to read into the church’s teaching on marriage.
Marriage exist for the primary purpose of rising children. In the fruitfulness of the marriage act, the very creativity of God is at work. Homosexual relations do not lead to this reality (in any real or proper fashion). Therefore the church teaches that “gay marriage” is not simply immoral but impossible.
In terms of you last question, you are entitled to your private doubts, but as you yourself said at time you may simply need to submit to the church’s teaching. I think if you look into it a bit more, you may well find yourself not only submitting but begin to understand the reasons for this teaching.
Catholics understand that the church has authority given it by God to teach on matters of faith an morals. This is a central tenant of the faith. While it would be unlikely that you would ever suffer any formal excommunication for privately doubting or dissenting from church teaching this is a poor way to look at things. Would you put yourself in a position of discord with the teaching of the church, the one organization with appropriate authority to teach on this matter and yet dare to think that you would remain in good standing with God?