Well long term depression is a pattern of action in your brain that is activated when it is required. So to increase LTD you need to provoke something (action or drug) to increase LTP and then your brain will selectively choose which part of your brain loses the action potential to stabilise your energy depending on the context you are in.
To do that My suggestions are supplementing on L-Glutamine and Glycine, I would also stop any NMDA antagonist since it only reduce LTP and consequently LTD. Tianeptine is not a serotonin booster it is a AMPA stabilizer and NMDA amplifier. So I think tianeptine is helping you. I would add Noopept and L-Theanine. That is it for supplements, As for actions I suggest you do alot of exercise and alot of work to make your brain want to create more LTP to act and consequently LTD to compensate.
As for the opiate withdrawl nothing can really help, your body needs to stabilize and it will not be fun, the only thing to do is tapper off slowly.
As for Zoloft My opinion is that it dissociate people and reduce the potential for conscious decision even if it is somehow good for the brain at the right dose and the right person.
It doesnt work for me so I use Mushrooms to compensate. I use them 10 times a year mabe more mabe less. They work by making every hesitation in your brain come out and speak out. So you are less ignoring parts of you that want things, know things and can do things, making you more you, temporarely, and when you come down its like landing a plane of thoughts in a land of personnality. You can choose which part of your personnality gain strenght and which give it. But there are limits its not a magic solution to every problems, it only makes you gain control over your thoughts and come back to your mental routine when you come down. But how to know which will make you happy other than try it?
I hope I could help you, if not I hope you will find peace somehow.