First of all, I can understand your frustration. I suffer from a similar (albeit less intensive) situation (mild anxiety and ASD).
The problem with your approach is that the Stack Exchange format is just not designed to take the user into account.
In contrast to a traditional Q/A or forum-style format, Stack Exchange aims to first create a library of high quality questions and answers with as little noise, discussion or pleasantries obfuscating them. This has worked well over the years, but it also means that the feeling, experience and yes treatment of the asker is secondary to the usefulness of the Q/A to future visitors. This means that Stack Exchange treats every post as standng on its own, ideally without considering the author whatsoever.
All community moderation is geared this way. You don't see context of what a user posted in review, you're not supposed to consider who posted what when voting, downvotes are anonymous and at the discretion of the users casting them, unless (and that's the only unless) you target them at a specific user. Yes, that means that I can go around downvoting everything I see when I have a bad day, but downvoting a specific user's posts in a serial way is a punishable offense.
Following from that is that the Q/A format here fundamentally does not permit exceptions or special considerations based on author status. That is a rough thing to grok - I can understand, downvotes and negative feedback can quickly feel personal (especially to someone with anxiety).
I also have problems being polite to people who are not so polite to
me and can sometimes end up embarrassed by what I say in haste, due to
personality disorders. I recently had an issue with a high rep SO user
seemingly playing strange games of commenting strange and rude
comments and then deleting them. I tried emailing SO for help but was
given a generic reply and just ignored by my further attempts to see
what I could do. Obviously I couldn't flag comments that had been
deleted. What is the best course of action to stop people from causing
my head to go in a complete spin by being not-so-nice.
I don't think you have any course of action here except trying to deal with the problem better on your end. Particularly
Commenting for people to take your condition into consideration is likely to be unfruitful, such comments are frequently removed as no-longer-needed or obsolete. Comments are only supposed to be used for clarification or direct actionable feedback or direct criticism on a post. Even those are regularly deleted after their purpose has been served. In addition to this you are likely to invoke a form of streisand effect (requesting that people do not down or closevote causes people to do it more, in any form).
Editing such a passage into your post would likely be removed as noise (posts are supposed to contain only material directly related to the question or an answer thereof). It also triggers the same streisand effect.
As you have noted, stack exchange staff is not really able to assist you when contacted about something like this, as its a function of their Q/A system and changing it to suit these purposes is currently unfeasible and undesired by the community.
Moderators can not do anything beyond deleting actual rudeness, for which there are dedicated flag types.
What you can do
Actual unfrienliness and unkindness or verbal abuse is against the Code of Conduct. This means that it is actionable by moderators. You can flag comments containing such as unkind or abusive, and if they are found to be by moderators, the comments will be deleted and if the user has a history of doing something like this, they'll be sanctioned.
Please note that even though something can feel like an attack, it's possible that it's just criticism. In that case moderators will not remove it or sanction the poster. I fall into this trap from time to time and have to remind myself to not take things personally. It's really important on here.