Just because your boyfriend's wife trusts your boyfriend does not mean that she is under any obligation to trust you - now or ever. But I bet as the relationship matures, she might be able to become more comfortable with your position in her life if you continue to be diligent about your own sexual health, love for your boyfriend, and respect for her.
She has every right to make boundaries within her primary partnership. You have every right not to like those boundaries. But the only thing you have CONTROL over is your involvement in the relationship. If your boyfriend is satisfied with the boundaries his wife needs to feel confident about her sexual health, you're welcome to be unhappy about it and discuss it with them, but I think it's unfair to expect them to change a boundary that they're both content with.
I don't mean this harshly at all, so please don't take it that way; I don't know you or have any reason to be mean to you or make you angry, so please see this as constructive criticism from an outside 3rd party stranger looking in. Your post sincerely reads as though you're villifying her in your own mind, and making her responsible for your sexual disappointment. Things like how "the feeling I get from her is "There is nothing in it for me personally, that my husband has these feelings from you and is sleeping with you. So I won't make too many waves, but I certainly won't like it either, and I'm not going to go out of my way to smooth the path for you two." and "I suspect that this has nothing to do with pregnancy and disease, and everything to do with her wanting to be the only one he really enjoys sex with".... Especially in that last quote, it seems very villifying. She has given an extremely reasonable explanation for why she wishes him to use condoms with other partners. She doesn't want her sexual health compromised. She might trust him with her sexual health, but I think it's a bit much to expect her to trust someone (you) that she doesn't know very well nor has any background from which to establish any trust.
My suggestion? Accept her reasons and words at face value, try to understand her and show her understanding and compassion, and try to build a foundation with her that could allow for the development of trust.
Oh, and if your reason really IS that you want your boyfriend to achieve orgasm, it might please you to know that I know at least two men who can, for a fact, achieve orgasm and ejaculation with a flaccid cock, and manual stimulation alone. Lube helps
If your reason is more that you want to be penetrated, bear in mind that lack of a condom would provide no guarantees. And I don't think that him wearing a condom with his wife is very helpful or fair, but masturbating with a condom is a great suggestion. You might also have him try masturbating with the condom on when he loses erection and can't stay in you. Encourage him, make him feel sexy. Losing an erection can make a guy feel humiliated and inadequate; if you can help him feel like he's still sexy and you still want him (and his cock), it could make all the difference. Try not to be disappointed, and try not to show disappointment. Channel that into encouragement and help him regain that erection while the condom's still on, and you might be able to pick right back up where you left off. State of mind can mean everything!