I think you probably really need to sit down and have a serious talk with your rheumatologist about all this. I can understand you being reluctant to take meds having seen a couple of bad examples with your friends, but I think you will find that for most people biologics are miracles that deal with all the things you are having the most problem with, and the incidence of those serious side effects is very small.
You are also in a health system that uses "evidence based" decisions on what drugs will be available for prescription, (and there are many drugs that NZ has declined). If the NZ health dept has decided to offer certain biologics, then you can be sure the risks and benefits have definitely been very carefully investigated, especially in the case of very expensive drugs like these.
I suspect that if you don't do something to really "treat" your AS, then you will be much more likely to achieve your worst case predictions of further increases in pain and disability. If you do start treating, then you could just as easily end up having a really good life with minimal disability and little progression.
Have a good talk with your rheumatologist - let him know ALL of your concerns, and then ask for his recommendation again. And then give serious consideration to going with his treatment recommendations at least for a trial period.
