She has a right to her safe sex protocols even if you don't like them. Even if you think you are safe. In my relationships, condom use is mandatory and it does not change with the length of the relationship, ED problems, or how important the partner is. If you were in a relationship with my husband, i would also tell you that it is the one thing that is not on the table for negotiation, period. Full stop.
That being said my OSO has ED problems. His have been getting some better with treatment. As long as he is satisfied, I am not going to worry about his pleasure. That is his to manage. I use condoms with my OSO. He has a wife who would not be comfortable. I have been with him for 15 years. Some boundaries you just have to accept or walk away. The wife is not wrong to need safe sex protocols, and have you never ever heard of a false positive or false negative on a test?
Sounds to me like you want to be primary. You want your wants and needs to be the only ones that matter. All I keep hearing is "but I'm safe...". So the fuck what... Just because you haven't killed anyone doesn't mean we should repeal the laws against murder. You seem to think that you are the only other woman he will ever want to date as well. Sometimes people hold their boundaries because they see the "bigger picture" and she knows by setting the precedent that her safety could well come under fire in the future.