Hiya and sorry to hear about the trouble! I am curious if you are intending the lambda to read from your site’s deployed files, rather than from a file deployed with the function? For the lambda paths starting with “/” are not “from the root of your website”, for instance - they are “from the root of what was shipped with your lambda”.
I think though you are trying instead to get the file into the function, right? And to guide you in doing so, I would have linked you to a comment in one of the posts you linked above: Hosting a file along with my function - #23 by Dennis . But I think you’ve maybe tried that already? Sorry to not be a pro in most of the technologies (typescript, functions, graphql) you use to be better able to understand your very detailed (thank you!) post in full.