Quite honestly, it sounds like your purpose in telling the aunt has more to do with your hope that she'll divorce her husband and he'll run off with you than with any real belief that she has a "right to know".
It's not your business to tell her. It's the husbands business to put on his big boy pants and confess to the wife. It's your business to keep your hands off another womans husband while they are still married.
I'm saying you need one on one psychiatric therapy, not an internet forum where you keep posting the same concerns over and over again. You need professional therapy to help you get over this obsession.
The diabetes itself should not cause difficulty with actual orgasm (neuropathy...nerve damage resulting in difficulty achieving an erection can be connected with diabetes).
When I was married my husband went through a period of about two months where he was unable to orgasm. Like your husband he could achieve an erection but just could not climax no matter what method we tried.
After the two months this passed and the particular issue never surfaced again. Jim was not a diabetic.
Eric...HIV has a very narrow range of transmission. It is a very delicate virus outside of the body.
People sometimes worry all the time about picking it up from inanimate objects such as toilet seats, door knobs, eating utensils, food but really, there are only a very few ways that someone can get infected as you've pointed out yourself.
The two main ways folks become infected is through unprotected sex and/or sharing of IV drug needles with partners who carry the virus.
Many women would prefer the water based products since the oil based ones are harder to remove, can stain sheets, should not be used with condom use (they can increase breakage) and may leave an odor afterwards.
In addition, some women are allergic to some of the vegetable oils such as olive oil (and my partner is allergic to coconut, including coconut oil).
It's probably fun to experiment with several on the market.