It sounds like this may be more than psychological. You already have been doing what I suggested, so a trip to a urologist may be worthwhile. I don't see how he could not get a stable erection with oral stimulation from someone he finds attractive. No, the insults will not work, but I understand your frustration and your hope that you could maybe make him angry enough to block any psychological barrier he might have.
Thanks very much for the advice. What you have described is actually what I have been doing over the last few months. He has times where he regains his confidence and is able to have intercouse. However, there also are times where he completely regresses even though I try to stimulate him in the manner you described. If I stimulate him orally in a slow, deliberate way and he is unable to attain an erection (this has happened several times in the past) does that imply a physical problem? I'm reaching the end of my rope and it's becoming increasingly difficult for me to remain patient. Admittedly, I have recently resorted to belittling him with insults, and I realize that this is counterproductive.
What he and you are experiencing is quite common and can be overcome with patience and understanding. Performance anxiety often leads to more anxiety if he is concerned with maintaining an erection at the same time he is concerned about pleasing you. He needs to get his confidence back so that he will know that he can maintain an erection and that he then can ejaculate. One way would be for you to stimulate him orally in a slow, deliberate, non-threatening manner. If his "plumbing" is working properly, it would be difficult for him not to get and maintain an erection in this way. Continue with the stimulation until he has an orgasm, if possible, so that he can gain confidence with the process. You may have to do this several times over a period of days or weeks before attempting p-v intercourse.