Have you thought about trying to find a decent psychiatrist to talk about your depression with? Don't go to anyone recommended by O'Neil, but maybe hit up your GP for a referral. A psychiatrist would possibly recommend the implant be removed, due to the risks associated with them (both in terms of depression, and also the fact that these implants have not been approved for human use in Australia). It also might be the case that you could benefit from some other medication (other than seroquel and temazepam).
Also, be aware that naltrexone reverses tolerance, so if you do decide to use again, your tolerance will be much, much lower than if you'd just had a break. This is the reason so many people died when the implants first came out. People can predict their tolerance (to some degree) based on past experience with short breaks etc, but the naltrexone reduces tolerance much faster than the natural reduction in tolerance that comes from taking a break.