You’ve already made it clear that you have:
- A broken Discourse installation, having deviated from the install guide
- Gaps in your technical knowledge in implementing the subfolder install.
Google make it quite clear that subfolders and subdomains are treated equally - as your don’t currently have the expertise to install this you probably need to consider making a post in the Marketplace.
And bear in mind that complications do arise with subfolders and updates - you’re going to need to retain someone to help you maintain it down the line.