You have a very good head on your shoulders, and this makes me reluctant to give unsolicited advice, but I think that what I have to say is important, so here it is.

I think you should never talk about this any more on this or any other forum, at least not for a few years. Just the act of confiding in a group where your husband does not belong can have a negative impact.

You found a happy equilibrium, so why not enjoy it? Changes at this early stage are risks. There is an expression in the game of bridge, you found a fit, why look for a misfit?

Any kind of relation where you both are happy is good. There is no inherent plus value in BDSM over vanilla or the reverse. If you migrate towards BDSM the vast difference in experience can affect your relation so you will have to tread very carefully.

You are in a delicate situation, but if anybody can pull it off it is you.