My ex-husband had a severe psychotic episode and was in-patient for over a week at a psych hospital last year, having "suicidal ideation, hallucinations, etc..." but eventually released. Is it very likely that he may have another episode. Eventually, he s

Relapse. The likelihood of relapse is dependent on many things including original onset of symptoms, family history, medical adherence, low emotional volatility in his relationships with friends and family. Things that can help prevent relapse is taking medications consistently, learning comunication and social skills, daily structure with physical activity, refrain from use of mood altering substances.
Of. Of course you should be concerned. Always listen to your gut; you clearly stated, "i am gravely concerned for our child under his care." if you feel like your child is in danger due to your ex-husband's medical conditon then you need to get the department of child and family services involved. You can contact them or local agency and tell them about your concerns and they will decide if an investigation is warranted (very likely based on your post). All the best.