The problem is, baptism is the duty of every Christian, but if they are not saved until they are baptised, then they are being baptised as an unsaved person, and only are saved after they come up out of the water. Most people's experience alone will tell them that this isn't the way it is. They were assured of their salvation BEFORE they were baptised. They were baptised in obedience to Christ's command, not in order to receive that which they already had the inward assurance that they possessed.
You're trying to make baptism a condition of salvation, when it is the sign of salvation already received. You think you know what those verses say, but you need to read them again, with a request to the Holy spirit to show you what they mean, which means you will have to let go of your preconceived idea, and let the Holy Spirit teach you.
"For" does not mean simply 'in order to bring about;' it also means 'as a result of' or 'because of'. Hence it is quite grammatically sound to say that to be "baptized for the remission of sins" does not mean "baptized in order to obtain the remission of sins," but "baptized because of the remission of sins."
The phrase "to the remission of sins" is not the same as "because of the remission of sins", and you know that. It is the idea of movign towards something, not looking back. It is the same grammatical construct as in Matthew 26:28, and yet you wish to have it translated completely opposite. Try again.