Yes your marriage will be tested. A lot will depend on how much support you are getting during the application process. Your partner will have to understand that becoming a RAAF pilot is like getting married again because it will take a lot of your time and your partner must understand that. Having said that, it helps to involve your partner in the various activities that come along. I and my partner had 10 great years in the RAAF without any problems in that area.
On another point, when considering what wing of the ADF you are interested bear in mind one very inportant thing - retiring age in the services is quite young and therefore you must consider your future beyond the services. So carefully consider which types of aircraft you might like to get experience on if you intend to go into civil aviation at the end of your service career. The right background is very important. For example; fighters and helos are no help for airline employment but can be useful in other areas.
Good luck
Have a nice day