What is the difference between the Domain and the Problem?

Using the gists my Relationship Story Domain comes up as "Considering Something Unacceptable". When I look at the Theory information is says "the heart of the problem" and "this describes how the MC and IC relate to each other in the story". When I look in All Topics to the left and click on Relationship, this Considering something unacceptable shows up in RS Domain, not RS Problem. When I click on RS Problem, the only choice is Equity.

Would that mean they start off thinking each other's attitude/response is unacceptable, then the IC changes? Does the IC change if the MC is steadfast, or does he just fade away? Would it make sense for the IC at the end to consider himself kind of equal with the MC, giving him a tip that saves him, before fading out?

It's a matter of scale. As a domain, the main conflict in their relationship will be a clash of attitudes in terms of considering something as unacceptable. A RS Problem of Equity means that the heart of the conflict in the relationship grows out of equity (fairness; balance). For example, a married couple come into conflict in their marriage when everything has to be completely even (if one set of inlaws stays for two weeks, the other set of inlaws must stay with them for two weeks (even though neither of them can stand spending time with one set of inlaws) in an effort to be fair.

If the IC is change, the MC is steadfast, and vice versa.