You're super paranoid, and hyper-focused on it, to the point of making it into a vast conspiracy theory (... about air purifiers?) with you at its nexus. I don't think I would characterize that as "great mental health."
That's not how this works. People who make claims are the ones who need to provide evidence.
You are making a claim. This claim centers on your being harassed by very many different reddit accounts. This, in itself, may be true, though not necessarily for the reasons you believe. This basic claim, standing all by itself, is not extraordinary. People harass other people online, and it's not out of the question that random internet trolls would pile on harassing someone who is making themselves an easy target.
You extend this claim by explaining that some guy who invented something on the iPhone in 2007(?) is himself making all of these accounts only to harass you. I do not believe this. This extension is extraordinary, and so requires an appropriate level of supporting evidence.
You could so very easily be completely done with whatever harassment the u/mustardman account receives (no matter the source) by simply abandoning that account. You haven't. Not only that, but the account you're using here is named exactly the same. You are actively putting yourself into a position of "fighting a just and noble fight against the scoundrel who unjustly attacks you." You are writing a story for yourself where you are the protagonist hero (who has connections to the FBI ... ?), and someone notable is the antagonist villain.
The solution here is for you to walk away, and not care about any of this. If you can - and do - do that, then you're fine. If not (and I predict you will have many explanations for why not), then this is a you problem.
Stop and think here. Who are you that makes you so important that someone is going to put that level of effort into harassing you? That kind of effort carries a relatively high cost in time, and in the opportunity cost of that time, which cannot be used for other pursuits.
Sure, gaslighting is a real thing that can happen. But it requires the target to be a more-or-less captive audience. Think domestic violence, employer-employee relationships.
You are not a captive audience. Your livelihood and personal well-being in no way depends on remaining connected to anyone harassing you online (whether that harassment is real or imagined). You are capable of ending the harassment at any time, again, by abandoning the account that receives harassment.
Your failure to take a simple, unilateral action to end your claimed harassment must mean that the harassment is important to you in some way. This is unhealthy, and is why you should seek mental health services. It is also plenty common for someone in a mental health crisis to rationalize their way out of recognizing it as such by believing that other people are gaslighting them. It's a shitty, shitty knot that brain fuckery does.
I will provide evidence when I am able, ...
Until there's convincing evidence to the contrary, I find it much more likely that you're experiencing a mental health incident that you should get treatment for. Let me be clear: I'm not calling you names or being derisive. If you complained of chronic chest pain, I would advise you to see a doctor. I believe your current complaint is symptomatic of a health concern, and you should see a doctor for it.
Who are you that makes you so important that someone is going to put that level of effort into harassing you? That kind of effort carries a relatively high cost in time, and in the opportunity cost of that time, which cannot be used for other pursuits.
If you read my report you would understand. This information is enough to destroy his company that credibly proves deceptive marking claims and other financial crimes. He was already mad that he had to spend somewhere around $400k or higher on third-party Intertek testings. He seemed pretty mad about it because he didn't think they were valuable.