You don't owe your ex any help. If you no longer have a relationship and contact from her hurts you, you have a right to cut her off. Are you staying in contact in hopes that she'll change her mind and get back together?

Sounds like they're really piling it on at work. The other programmer has a right to look for other work, yes. However, you have a right to talk to him or tip off the management so your job can start the process of hiring someone else. Hopefully they can find someone in a short time; there are a lot of qualified people seeking employment. I'm sure it will be rough during the transition, though. That stinks.

Try to be kind to yourself and make time to recuperate. Maybe if you do it will be easier for you to concentrate when you are working. It sounds like you have a lot of worries about things that you can't really control. Are you able to see a therapist? Do you keep a journal to get your worries out? I hope you're feeling better and you get some peace this weekend.