There's more here to be "worried" about than other females possibly being pursued, or his feelings toward you diminishing. And that is - he is unwell. He is a possible danger to himself and/or others. If there are any family members of his that you can contact, perhaps you should let them know what is going on in case they are unaware.

Another area of concern:
Most people who are in relationships with bipolars certainly wouldn't use the word "comfortable" when describing those relationships. And being "insanely jealous" is not indicative of love.

He's mentally unstable, you admittedly aggravate his condition. Do both of yourselves a favor by hoping he will not come back, and if he does, do not engage him.