If you like him enough for him to be a distraction from your ex T then fine, but that doesn't seem to be the case. So I would not sleep with him since your whole heart (and mind) are not in it and you might feel worse. Sex also seems to mean a lot to you, so I wouldn't do it until you feel 100% sure.

I also think very strongly that you should see a female T and not go back to or have contact with your ex T. I know it is torture for you, but cutting off contact is the only way to completely get over someone. Your identity right now is so tied up in your feelings for your ex T that your sense of hopelessness gets worse every time there is a bit of contact with him. Right now it seems like you are ruled completely by emotions - to the point they are ruling your decisions and keeping you from moving forward with the rest of your life (and I'm sorry if this is wrong, it's just how it comes across from your postings). You need a good strong female T who can help you get control over your emotional self. Remember, sometimes the hardest things to do are what are best for us.