Sounds like you met a girl on craigslist, connected gloriously, fell in love, and then started getting insane and false messages from her suggesting she was dying or raped or pregnant and other things that provoke a similarly intense emotional response.

You started noticing the stories were sounding fishy, and from investigating her stories you were in at least some cases able to confirm that they were definitely false.

She repeatedly put you into situations that made you feel awful. It kept going like that, and you saw her from time to time, but it was really messed up.

There was an on again off again thing where you'd get fed up and she'd beg you to take her back, and you'd accept.

You had pretty awful experiences with online dating, including a point where you went into detail with a girl about how you loved her profile and she berated you, saying things that made you feel horrible.

You are 445 pounds, you want to find love and connection, but you feel hopeless, empty, and detached. Your family is consistently overweight and you are terrified of negative outcomes in life.

You're trying to distance from your ex, but she keeps on stalking you and making you feel horrible, including shoving her success in your face and telling you to kill yourself.

In response to all of this, my guess would be that your best course of action would be to do what you can to distance from your ex and do what you can to improve your quality of life.

You've got some pretty rough stuff to deal with. Ensure that you have a network of people who care about you that you can talk with to make these things easier to deal with. I would think that facebook could be a good way to go. Maybe there are groups for people who are/were 400lbs+ who you could connect with and feel a sense of connection with? They would likely be familiar with these same struggles, and it might help to see this.