Ding, I fully understand your frustration, however here is my advise:
1. If DHA tells your case in processing, there is nothing much you can do but wait. I had a similar situation with my PR which took over a year to process. Sometimes you just really get unlucky with an officer, which causes you much more delays than it should be. I've been there. Yes it is unfair, but nothing to do about it.
2. Even if you get approved right now, I doubt things will go fast - my friends who had their ceremonies cancelled a day before it supposed to be (due to COVID) are still waiting for any information.
3. Good strategy right now is just unwind your mind and forget about the process until they notify you.
I attached the processing time at this moment, and as you can see from the date of application to decision it is 15 months. Considering your overseas case you are most likely in that 10% which can take longer. I also bet you are not alone, and there are thousands of people stuck just like you, not aware of this forum to share same story.