You got some good info from previous poster though I have heard the number can actually go up to close to 20,000 a day. I will also add that I have read that around 40% of the population gets ectopic beats on a regular basis. Stress is indeed the biggest culprit so anything you can do to try and reduce your stress will do your heart good. Yoga or meditation or even just reminding yourself to do deep breathing when you feel stress coming on will help you greatly. As well also address any stomach issues you may have. They are a big trigger especially after eating meals high in carbohydrates or spicy foods. As for the runs you are feeling if they convert after just a few beats like the other poster stated you likely need not worry especially considering you had your heart checked out and evaluated to be healthy and sound. So just try and do your best to not let the extra beats rob you of your happiness. Do not give them any more attention then they deserve meaning only pay attention if you notice things seem to be getting to a concerning point. Take care and know you are not alone. There are many here dealing with loads of ectopics as well.
1. I don't know that there is a 'normal' amount of pvcs in a given time period. The majority of people are not aware they have them at all even though statistics say almost everyone does in fact have them. However, while not 'normal', I have read that under 1,000 in a 24 hour period, a doc would not be the least bit concerned with. And supposedly, they must number greater than 10,000 in a 24 hour period to become a concern in terms of weakening the heart. Short answer, under 10,000 per day is generally considered fine by docs from my readings.
2. Runs of these beats greater than 3 are considered either svt (if it's pacs) or vt (if it's pvcs). If it were vt, it would be something you'd want a doc to know about but still probably nothing dangerous if your heart is healthy. Vt can be dangerous but I believe is generally not in healthy hearts and when it quickly terminates (which it sounds like your does).
3. It sounds like you are just like the rest of us on this site and have premature beats which is definitely normal. Another common theme is that most people with these beats also have anxiety which doesn't help anything. You'll find there are people who post on this site who have the premature beats all day every day and are no worse because of it. If the docs say your fine, it's best to believe them and relax!