Seattle Children's Hospital has a wonderful series of "When to call the Doctor" information pages - they're well laid out, informative, and easy to use. I find them very helpful when trying to decide if/when to call the pedi about a medical concern (Google "Seattle Children's" and whatever symptom you're interested in, and they'll likely come up)
For fevers:
https://www.seattlechildrens.org/medical-conditions/symptom-index/fever
and other symptoms:
https://www.seattlechildrens.org/medical-conditions/symptom-index
HTH
Re: s/o PSA: Great resource for "When to call doctor?"