I don't think there's anyway a person can know how stressful the job is without doing it for a few years and running some terrible calls, I sure didn't...but you didn't want advice on that so against my better judgment I'm going to skip that part.
First, I would be super careful posting about depression/suicide if there's ANY way the post can be traced to you. Police departments do online searches of your name and some are VERY thorough.
Question 1-I've worked for about 4 different EMS agencies and besides asking how I handle stress nothing about depression or mental health has come up.
Question 2- If the department requires a physical exam the meds might come up, I've worked with several people who were on anti-depressants and it didn't interfere with them getting hired in EMS.
Question 3- I recently went through the sheriff departments hiring process, and it is VERY intense. You do a long background investigation and they contact quite a few people.You also have to pass a psychological evaluation where you meet with a psychiatrist. Mine asked me different questions about stress and how I deal with people and situations, it got pretty detailed. I spent about 20 minutes talking to him, I don't know how your history would affect this part.
Good luck with whatever you decide.