Welcome to the community
Seeing a therapist is a great idea and a good step, since like they say... kink can be therapeutic, but it's not therapy. And depending on where you are and what health coverage you have, you may be able to find a "kink aware" therapist who might be able to discuss things with you in that context.
As for sex... for many (though certainly not all), a cornerstone of BDSM is in the power exchange dynamic. And while sex can be a part of that power dynamic, it is absolutely NOT a requirement for living a kinky or bdsm life! There is no "one right way" to do all this, so if, FOR YOU, a certain set of activities is currently off the table, that's totally okay. And if someone tells you that you're not a "real" this or a "good" that because you have these limits? Walk away and find someone better.
For your partner... maybe they would consider attending some therapy sessions with you? Or you both might go to a couple's therapist? If they are worried about triggering you, then maybe having a professional in the room to guide the discussion would be helpful? Your partner may never be exactly what you want in all things, just like you may never be exactly what they want in all things, but there is a really good chance that you can both be good for each other if you can build a relationship with a lot of open communication on top of a foundation of mutual love/consideration/creativity. That eventual relationship may not look like what you're imaging now, for example... maybe you really want him to X, and he just isn't comfortable with X no matter what. But maybe he'd be comfortable with holding you while you did X on your own, or with someone else? Or you'd be happy doing Y with him evenif you couldn't do X? Keep that whole "there's no one way to do this" mantra in mind and if something works for you and your partner? Then that's the thing to do!
And then your last question is kind of a blend of the others... yes, you can absolutely be married to one person and in a power exchange dynamic with another person. And you don't "have" to do anything in any relationship that violates your limits, up to and including whatever activities you define as sex. Sure, some potential partners are going to be off the table if your needs don't mesh, but then... your needs don't mesh, so keep them as friends and move on. Open and transparent communication can be hard, but it's the best way to ensure that your needs, your partner's needs, and your possible play/power exchange partner's needs all line up.
Have you explored any podcasts, youtube channels, or books? Podcasts/YouTube channels like Loving BDSM (with Kayla Lords and John Brownstone) or American Sex (with Sunny and Keen) can be a good introduction to how bdsm can play out in a married couple (including how polyamory and online or in person power exchange relationships outside that married duo can work). And although they're older, books like The Ethical Slut by Easton & Hardy or Opening Up by Taormino are fantastic for exploring all the ways relationships can grow, and since they ARE older you can probably find them at your local library (check their ebook offerings if you prefer that anonymity, or ask for an interlibrary loan if they're not available locally). These are all things you could share with a therapist, or with your husband, to get a conversation going.
Good luck, and again....welcome to the community! I hope you find what you're looking for.