That's a pretty good summary. Some cheap economy AA fares do allow date changes at a fixed fee provided the routing stays the same and the fare class is available on the new dates, but this is the exception rather than the norm, and I'd guess the agent would have said so.

Beyond simply forking over money, options include:
1. Say "no, what's booked is booked" to your future spouse.
2. Sit tight and hope for a schedule change. In that case you might at least avoid change fees (but not fare recalculation).
3. Review your entire itinerary before calling AA and have a definite plan. When you make a change, the whole ticket is recalculated as if purchasing anew. Thus you can check the cost of the new itinerary yourself by looking on AA.com, kayak, or whatever. The additional cost will typically (again, depends on fare rules, this is a simplification) be new fare minus paid fare plus change fee. For example, it would be worth checking MCO-DFW-NRT-HKG-DFW-MCO, and then a separate HKG-DPS-HKG ticket (or NRT-DPS-NRT ticket), or try MCO-SIN or MCO-KUL. How you could do this is a whole subject in itself.
4. Look at purchasing one of the OW fare products such as Circle Pacific. These tend to be fairly uncompetitive in many cases, but if you are starting to look at $5-6000 in economy they're worth putting in the mix.
5. Check the fare rules about changes after departure versus before departure.