I am terribly sorry to hear about your health travails, and I very much hope that one day soon you will receive the right diagnosis and thus the right treatment. I'm sure that both can be obtained in New Zealand, or else in next-door Australia.
There are a number of chronic swelling disorders out there, and you are obviously suffering from one of them, but from what you describe chances are that, for better and worse, you do not have SCLS, and so IVIG may/not be the proper or best treatment for you.
*I have 3 constructive suggestions for you.* First, persuade your doctors to measure you and your blood for 3 objective conditions on a daily basis before, during and after one of your swelling cycles: hypotension, hemoconcentration, hypoalbuminemia. (It would also be good to test you a couple of times for the presence or not of the MGUS.) For an explanation and further details, see yourself and have him/her read the tab "Disorder Details" in this website.
Second, read yourself and have your doctors read the article that is listed in first place under the tab "Disorder Resources": _"Narrative review: the systemic capillary leak syndrome,"_ by Kirk Druey and Phil Greipp, see https://www.ncbi.nlm.nih.gov/pubmed/20643990
The full article, which I'll gladly email to you upon request to email@example.com_, has useful tips for how to identify SCLS versus other conditions.
And third, have your doctors send via email your medical history with as much detail and as many lab results as possible to the world's leading authority on SCLS: Dr. Kirk Druey at the U.S.National Institutes of Health, email address firstname.lastname@example.org_, requesting an opinion (consultation) on your case and tentative diagnosis of SCLS. He should be able to guide them and, if you don't have SCLS, to suggest other relevant diagnoses for them to confirm.
Let us know how things turn out, OK?