HPPD will go away if you completely abstain from psychedelics for a long period. When I used LSD and other psychedelics heavily on a regular basis I had it and now years later don't.
I always preferred acid to mushrooms and never thought much of psilocybin microdosing but it works great for many. It seems to help with brain fog too that can be caused by amp/heroin abuse. Also potential neurogensis and neuroplasticity at even a low dose.
As a heavy poly drug abuser psychedelics are now sometimes a trigger for me to go off the rails a bit. I will go from a long period of sobriety to suddenly enjoying the euphoria and wanting to trip all the time. It can take weeks to come down from this. I'm in two minds if this is a good thing as the binges lead to sobriety in the end and not daily use of something. But there is a risk of the problems that can arise during the binge.
Whether you trip or not, focusing on exercise, supplementing vitamins/magnesium/etc and working on integrating new things into your life will put you in a better position than any kind of trip on it's own. I would try and undo any of the brain fog caused by abusing the amp/heroin before tripping or start with a low dose. Lions mane, ashwanganda and other medicinal materials also now seem to be the new trend rather than microdosing psilocybin. There is great extracts combining multiple mushrooms but I would recommend trying each individually first before combining. Lions mane is most popular.
This is a strange period in society, we are extremely unbalanced and outside our normal way of living. I have found sobriety the best way to stay grounded. Find someone you can talk to about this in real life if you can, things might not be as bad as you think. It sounds like this is still early days from your amp/heroin/meth use - things will improve if you abstain and focus on making as many positive changes as you can. You appear to have good self-awareness which reinforces that there is no reason you cannot bounce back and undo damage but be prepared for nothing to happen overnight.
I'm not an advocate of SSRIs personally but I know of a number of people who were also heavy poly drug abusers, experienced trauma and are having good success with a very low dose of Citralopam. I would not encourage anyone who has experienced severe trauma on a psychedelic to use that psychedelic again without a therapist anymore. I have seen people regress into horrible trips after taking LSD again after a bad trip even years later and they come out worse than they were before. Without someone to help you integrate it is a much riskier move than just focusing on abstaining and better health.
Also worth warning that ketamine dosed regularly seems to induce mania and bi-polar like symptoms. Can take about 2-4 weeks since the last dose before it stops. The world can seem very dull a few days after ketamine.
I've had success with revisting psychedelics after trauma but rather than regular dosing it's a high dose of something as an attempted reset or one off. Can help if you need to grieve or see things from a different perspective. It wouldn't be the first thing I'd do when feeling bad though, tends to be the final option.
I'm pretty adverted to SSRI's as well, I took them when I was like 12, and the brain zaps sucked. the only other time i tried one recently was for like 2 weeks and it gave me worse anxiety so i stopped. the sexual side effects i heard of also put me off as im trying to get a new girlfriend eventually (not that im in any state to, but do have hope i can eventually hopefully sooner rather than later). I've had mirtazapine really help, but the side effects weren't worth it, and the withdrawal was miserable (this is also what puts me off of psych meds in general, i find in my experience, even in some close friends multilpe who have died since, and others ive read they can tend to make shit a LOT worse). I might consider meds again in a few years or even a year if I can't get it together. But i'm not convinced microdosing (or even like, 1 gram a day) of mushrooms and a monthly mescaline trip for a while. I know I can handle that, especially if I have some benzos on hand. which brings me to my lsd trip, i absolutely loved it and it was a huge part of my life in like 10 years.. ive come close to (and kinda did) get the molecule tattooed on myself, lol.. anyway, i think hiking 8-10 hours into the woods on an isolated trail in the mountains and taking 100ug by myself there couldnt be any danger really from what i can tell, especailly if i keep some antipsychotics and benzos on hand. might be good with a trip sitter, though i think at this point (or that point, whenever it may be) unless it was someone i truly trusted like my imaginary new romantic partner, even then, it might be better, and safer alone. its definitely an experience ( the bad one ) that i want to transmute.
as for ketamine, good racemic or even s+ isomer K, if it is real, usually helps me out of a bad rut. i've considered getting one soon, though last time with that was a little traumatic, and the stress mixed with binging on amphetamines the day before led to a state where i was hearing voices for a ltitle bit, but i was also dealing with some serious gaslighting at the time, i've never had an issue with K before that other than getting a little too fucked up, and i was aso consuming extremely high doses of pure delta 8 distillate at the time as well as recently quitting antipsychotics. it may have been a dosage issue as well, i never use K more than once a month (maybe 2 or 3 if im going to festivals, but its covid time) in my typical setting, and usually no more than a gram, last time i did an eightball.
i agree sobriety is the best way, and thats mostly my goal, most days I just use THC, but i do take benzos occasionally (i mean, who with PTSD doesnt?) a few times a month, have been drinking occasionally but i've stopped that as it was just making me more miserable even in extremely moderate doses. i know for sure stimulants arent the answer and will make it worse, so i dont do those (which i think is what caused my manic symptoms i used to enjoy after a good acid trip into a psychosis sort of thing - once again never triggered by psychedelics but i even had one psychosis from depakote toxicity inside a rehab, so i dont know i feel another i could like, die), and opiates are way too overpowering to be useful because addiction potential is too high.
idk though i just want to get back to my normal, confident, hopeful, silly, outgoing person i once was, maybe it was cuz i was always in a relationship and im just lame now, usually flat affect, and resting bitch face and come across quiet but when i hit it off with someone about my few passions/obsessions i get manic energy to chat, or i used to anyway. but i used to not give a fuck and just be loving and happy and kind to every stranger i passed. now im all interoverted and frankly miserable half the time. psychedelics are what brought me that. but i am terrified of their sheer power as anyone should be and i havent had the set or setting to partake. my life is a *little* better now and in a few months i might be able to again.