3 hours self-connect with Southwest is cutting it pretty close but you can probably make it to last boarding call assuming everything goes smoothly.
6:30 AM arrival means you should finally taxi to the gate near 7:00 AM. After that, you will walk to FIS which will take about 10~15 minutes, longer if you are at the back of the A380. You can clear FIS pretty quick - it is all self-service scanners now for US passport holders so you should be done with it in 30~40 minutes. Much quicker if you have Global Entry obviously.
The big delay will be customs. If you have checked bags, it is completely unpredictable... it could be there waiting for you or it could take another 45 minutes before your bag show up.
In total, I think you need to assume 60-90 minutes to clear FIS and Customs.
Then comes the fun part self-connecting with Southwest...
QF won't tag your bags to Denver so you can't re-check it after you exit custom. You need to take it with you.
TBIT to T1 transfer is the worst possible transfer at LAX - it is one of the longest walk OR one of the longest bus ride. Walk will take you about 25 minutes at leisurely pace. Bus will take you at least 30 minutes during peak departure domestic departure hours at LAX. Expect lots of traffic. I recommend walking if you are able bodied person.
You will probably get to T1 at around 8:30 AM and the place is going to be a zoo with check-in lines out the door and TSA queues overflowing to the ticketing area. You need to check-in and then clear TSA so give yourself at least 1 hour to do this.
You should make it to the gate just as they are finishing boarding for your 9:25 AM departure.