content disappearing minutes after it’s published

It is true that this problem will need some extensive (and knowledgable) hands-on to fix.

In general, though, I would

  • disable all caching, including any that JetPack does

  • use my hosting File access (or FTP) to edit/change htaccess

  • change all credentials – WordPress, hosting, FTP, databases – resetting all passwords to different (and strong)

  • reinstalling (manually) WordPress (from the admin/updates), updating everything else (themes/plugins)

  • using FTP (or hosting file manager) look at all folders for unknown files (sort by date to find files that ‘stick out’ because they are different). Do this after you change credentials

All of this will take time (and some expertise), so if you are not comfortable doing it yourself, then find a competent WP guru.

Good luck!