Vedic Hindu marriage is viewed as sacramental, which is a lifelong commitment of one wife and one husband. It is the strongest bond between a man and a woman, which takes place in the presence of their parents, relatives, and friends. This is an irrevocable commitment for a lifetime. Source

A women's place is at the feet of her husband. I don't need a source for this.

Raavan couldn't have done such a deed because he was cursed. Source

I didn't say he raped her. But questions were raised right?

A virtuous king's first duty is always towards his people (Rajdharma). In simple words, a good ruler wouldn't take measures his subjects wouldn't approve of.

Seeta in addition to being ram's wife was also one of his subject. Where was Ram's rajdharma to his wife and children? Ram's rajdharma was to do the right thing not to blindly do what his subjects demanded. What kind of subjects were these who still doubted seeta after she walked through fire?

forever earning a blemish on his reputation and knowing fully well that he would be misunderstood for ages to come.

That's the point everything he did was for his reputation. He didn't want to be called a cuck so he banished his wife, not for anything like rajdharma. If he was interested in rajdharma he would have worked towards reforming the thought process of his subjects.

Let's face it by banishing Seeta he solidified his subjects belief that she was raped. It definitely didn't help seeta's cause.