Can Apex Install Non-Virtual Resources via Assimilator?
Yes you can.  First, you can include non-virtual resources in your deck, since there is no restriction on this.  Then, the rules reference says the following on facedown runner cards:


  Runner cards that are installed or turned facedown do not have a name, type, or subtypes, and their abilities are not active.


Since you are installing the resource facedown, it is not a resource and thus not subject to Apex's install restriction.

Finally, turning it face up with Assimilator is not an installation, so is also not subject to Apex's restriction.  Support for this can be found in the rules reference:


  Turning an installed facedown Runner card faceup does 
  not trigger install effects