Can severe anxiety and isolation cause delusions/hallucinations?

Yes, isolation and: anxiety can trigger temporary delusions and hallucinations. A mental health professional can diagnose you and help you determine if this is the case or if some other condition is present. Peace and good health.

Yes: Very much so! Humans are largely very social beings by nature, and are in need of at least some interaction. I remember one of my professors during my undergraduate years who said to us: "If you were isolated from all human contact for a prolonged period of time, you would get weird." Very much so!