#1 yes, we know what sort of romance happens on the battlefield.
War bride - Wikipedia
#2 This not a child. This is a woman. That is written in the law.
#3 If a woman has no hope for supporting herself, she can absolutley consent to trading sex for money, housing, or food. That's called prostitution. When a man is caught with a protitute, he is not prosecuted for rape. Even if she is a poor homeless helpless being, and the man has the money and is able to help her. She consents to sex to support herself, has no other option, it's a different crime altogether.
#4 If it's about popular opinion, then your idea about "tricking a Hebrew slave" is a fail. I have found nothing online anywhere that shares that view. As I said, it's creative. But doesn't quite fit.
#5 Any opinion I bring which supports my view will likely be immediately hand-waved away claiming it's apologist. But, here you go anyway:
The Captive Woman at the Intersection of War and Family Laws - TheTorah.com
Deuteronomy’s law of the beautiful captive woman protects the non-Israelite woman taken in war from rape and from being re-enslaved after marriage.
To put it another way, the “take her as a wife” rule comes to forbid Israelite soldiers to rape captive women.
According to this approach, Deuteronomy wishes to protect the woman from rape, and to make sure she is well-treated if he marries her
The Torah is concerned with the soldier’s integrity both at war and back home; at war he must not rape the captive women, and at home, once he marries the woman, he must treat her like an Israelite.
While the Torah is far from egalitarian, it does not see the woman here as chattel; it worries about her treatment both as a captive and as a wife
https://www.chabad.org/kabbalah/article_cdo/aid/3416826/jewish/The-Beautiful-Captive.htm
she would have to shave her head (remove all foreign philosophies and ideas), cut her nails (eliminate excess cultural "baggage" and emotions absorbed from a foreign culture), and get rid of her seductive dress (the "garment" made of evil thoughts and transgressions). Then, she would have to mourn for her father (G‑d), and her mother (Knesset Yisrael, the source of all Jewish souls) and cry over her sins for a full month.
Then, and only then, would the Jewish warrior be capable of deciding what was the right course of action to take – whether to marry her or to send her on her way in a respectful manner
#6 There is an example from Torah that confirms marraige is consentual. Genesis 24:58.