Welcome to the forums! I'm so glad that you've found us here and reached out to share a bit about your situation. I'm so sorry that you're stuck, not only away from your partner but with your ex nonetheless! That sounds awkward at best and maybe even unhealthy at worst. Do you mind my asking how you two get on? Do you feel safe around him?
If you feel comfortable sharing that, I think the answer will go a long way to helping you figure out what the best move is going forward. In the meantime, are you able to talk with your partner via video chat, phone, or text/email?
While I /think/ at this point intra-state travel (from one part of QLD to another) is allowed, i.e. as long as you are not crossing a border, all travel is discouraged and any travel decision is a very personal one based on your individual circumstances. I think that if you end up explaining your situation (i.e. stuck with an ex, especially one you do not feel safe around), any reasonable person would find that a more than adequate reason.
Please feel free to keep checking in here! We want to make sure you're well and safe, and have some other people to talk to if you want :)