Sweethometexas,
It does sound as if you have run the gamut of options that you have to entice him to explore your anal orifice, and your interest in enemas. Candidness is always best, as is honesty; and, sadly, he gave you the same when he said the anus is an exit, and not an entrance.
There is an article on this website, Klismaphilia ~ A Physiological Perspective; Jeremy Agnew discusses both the physical and many of the psychological aspects of the enema. Maybe there is something there for you.
It is my thought that another opportunity might come your way to get him interested in anal play, which may lead to sharing the enema experience. If you can very slowly start to explore his anal orifice during your intimate time together, he might find it a sensual journey. The prostate is accessible through the rectum, and if you ever got a finger on it, that might be like turning the ignition key in a car. I think trying to slowly make him aware that his anal opening can be an erogenous zone, and proceeding slowly thereafter if you get positive feedback, might be your best bet.
I wish you luck, as it can be terribly frustrating to have an esoteric interest of this nature, and not even be able to share it with the one person that is closest to you. It has happened to all of us at one time or another; and sadly, too, some people have never had the opportunity to share with a spouse, boy or girlfriend, or significant other, or just talk about it with another live person. Patience is always perfect for this type of situation, coupled with plenty of lubricant if he gives you access.
Yea, help him to discern his own anal sensitivities, and that may be the beginning of creating his interest, which would hopefully lead to your getting the enema you want. Or??? Is it the enema you deserve?
Be well... SensualSwitchTx
P.S. Please feel free to IM me on yahoo if you would like to chat some time.