You're right, it's a risk. But a calculated one if you choose a subject that is in higher demand in Australia. And weigh that up against the possibility of carrying on as you are.
It's entirely up to you how you go ahead and do what's right for you. But you have to accept that immigration is a contentious issue wherever you are in the world and trying to work the system is going to generate the sort of responses you've had so far. Most people, whether in Australia, UK or wherever welcome skilled immigrants and their families where they've worked hard to bring something to the country. Most of the people here have done what you say you are not willing to risk in order to get here which is what can be a bit annoying.
But like I say, it's entirely your decision which way to go. Whether the way you're currently doing things is right or wrong is only up to immigration to decide, I'd just feel very vulnerable in your current position and unfortunately there isn't a quick fix