Remove the Hotfixes. For Plone 5.0.2 you need no Hotfix.
The unified installer for 5.0.2 is here: https://plone.org/products/plone/releases/5.0.2
You should use that. I don't think it is experimental or unreleased.
use_content_negotiation should by all means be there in your site unless it got removed somehow. If that is really the case then the change in the code that @tkimnguyen mentioned will help. If it is really gone your might not be the only case and we'll change the code in the upgrade-step accordingly.