Can I log PIC instrument time in a sim without a current medical or flight review?
You can log training time in a simulator but you can't log PIC time.

The rules on logging are in 14 CFR 61.51. There's no requirement anywhere that I can see to have a medical and/or flight review in order to log time.

Logging training time in a simulator is allowed by 61.51(h):


  (h) Logging training time. (1) A person may log training time when
  that person receives training from an authorized instructor in an
  aircraft, full flight simulator, flight training device, or aviation
  training device.


But, you cannot log PIC time in a simulator. 61.51(e) says (emphasis mine):


  (e) Logging pilot-in-command flight time. (1) A sport,
  recreational, private, commercial, or airline transport pilot may log
  pilot in command flight time for flights-


That means, the only way to log PIC time is in an aircraft.