"You have heard that it was said, ‘An eye for an eye and a tooth for a tooth.’ 39But I say to you, Do not resist the one who is evil. " - That alone overturned a large chunk of the law code as it was all written with equality of harm in mind.
"Owning" people that submit themselves voluntarily for 7 years is not wrong. It is akin to our modern contractual labor agreements. When you get hired on a fish boat you are hired for a week, when you get hired as an actor you are obligated for years. Unlike with Actors you can actually get out of this agreement. They could be purchased back, or buy themselves back, or run away and not return without any worry of being caught. The Bible even says some of these servants loved the master so much that they committed their entire lives to them. Israel was Camelot. Think about it as someone being poor and destitute. You can't get a job because you need a place to live. This was an opportunity for people to get room and board and a paycheck and get back on their feet. It is nothing at all like the rest of the ANE. I am sorry but there is nothing wrong with voluntary servitude at all. If I was poor and homeless I would love such an opportunity.
Think about this...If Israel were mistreated slaves in Egypt, and Moses fled Egypt because he killed a man beating an Israelite slave. And Moses wrote this law regarding servitude. Why would he institute the same system as the ANE? He wouldn't, and if there is ambiguity in the text it should lean in the direction of the circumstances Israel was coming out of...real slavery. You don't even need to believe the historicity of that, it is in the same progressive narrative. You could believe the Bible was a complete hoax, but textual criticism would still require you to lean in that direction because both events are in the same narrative.