Dwayne, that was an excelent post and there is nothing I could add to make it clearer.
brneyes, the port charges, taxes and grats are on all cruises and all cruiselines regardless of promotion and will not vary on a particular sailing regardless of category (well, with one exception (Some lines have higher grats for suites to pay the concierge and/or butler). There are some places that you can with a single click, check on rate code promos and avoid all the calls and trying to get at whether they're available or added to a sailing. I however, have a vested interest in one such site so cannot elaborate.
It can be frustrating trying to identify when rate codes change that would be beneficial to you. Then finding out if they will allow such changes. They could easily program it where it was easier but that would ultimately result in a lot more clients getting their rates lowered after booking. That is not now and I doubt ever will be a high priority for the cruiselines to give back money, credits and other amenities as things change. Good luck with the process and it does often pay to do some checking.