I'm not sure I've got a huge amount of advice for dealing with a bipolar spouse. If there's a panacea for it, I've never figured out what it is. At some level, to be married to someone who is bipolar, you have to be the sort of person who can roll with the punches and keep breathing.
I mean, even if we take infidelity completely off the table, my wife has said some horrific shit to me over the years when she was manic. If I wasn't someone who had a pretty firm grasp on my reality vs. her reality, that could have fucked me up.
My wife got her diagnosis shortly after D-Day (12 years ago), and she's been really careful about managing herself. With this most recent episode, I was a bit slow on the uptake because it's been so long since she was manic. It took a couple of long, sleepless nights for me to put my finger on the feelings of unease I was having -- dealing with some actions that I won't elaborate on here, but that were completely out of character for her. (I think of those as my "Who the fuck am I married to?" moments.) Ultimately, it took slowing down my own emotional train and recognizing my feelings and the times in our marriage when I'd felt them before to open my eyes to what was going on.
(And then finding the ballsack to actually do something like drag her to her psychiatrist. Which was terrifying- - consciously taking an action that you know very well might just flat end your marriage and blow up your home if it doesn't work out. It's harder than one might think, and there's no way of backing out of a blatant statement that essentially says "I think my wife is off her nut". Most of us don't go actively looking for those sorts of moments. Given that you dragged your wife off to the hospital, I'm guessing you also know that feeling.)
When you're married to someone who is bipolar, you can do the 100% right thing for the situation and for them and you're still going end up bruised and bloodied for it (not literally). And then accept that your spouse probably won't ever clearly remember what happened during that phase, won't be able to connect it to their own emotional experience of their own life. With this most recent episode, my wife didn't even ever apologize for all of that shit. She got right and she moved on. The things that she said to me and things she might have done are my memories to carry alone. You have to get good at that, too, because no one is ever going to validate your experiences. Your spouse is never going to look at you and say "You pulled me back from the brink and saved us before it all went to hell." I've heard it said that bipolar folks tend to remember emotional truths rather than factual ones. Which means that what my wife remembers is that she was angry with me and I made her do a bunch of shit she didn't want to do. I was the over-reacting asshole raining on the parade. That's the image of me that's likely to stick in her head when she thinks back to the late summer and early fall of 2018. The actual things said and done are just footnotes, if they're remembered at all. You have to know your own reality and be able to patch up your own wounds and carry on.
You probably know that given how long you've been married, but you've never consciously thought about it as a life skill. Having an actual diagnosis helps with that instead of just being stuck with the vague sense that your life is unpredictable and occasionally out of control. It also helps with being able to avoid internalizing some of the shit you've learned to endure as just a "normal" part of being married. I'd like to think it's love that keeps it all together, but I suspect it's more just a commitment to doing the next right thing for you and your family, no matter how hard that is.
If you haven't done it yet, I suggest you start reading up on bipolar disorder. While it doesn't excuse anything, I found a great deal of comfort in learning about it, because suddenly whole pieces of my life experience started making sense in ways they never had before. (My wife is Bipolar 2, which is probably the case with your wife, as well. If she was Bipolar 1, you would have figured it out long before now. Bipolar 1 tends to have more extreme delusions that are clearly outside the realm of objective reality. Bipolar 2 is more of a generalized set of crazymaking patterns and behaviours.)
I'm trying to find a way to talk about this that doesn't sound like I'm just bashing my wife, because I really don't want to do that. But I'm also not letting her off the hook by making it sound like I'm fighting some third party force that takes her over and makes her do some terrible, hurtful, soul-destroying things. There's not some hidden *her* inside there that needs to be saved by some miraculous exorcism. She is what she does, and she's done all of those things, and the struggle of a spouse of a mentally ill person is finding a way to love them through that rather than in spite of it. As the old saying goes, you have to learn not to take their actions personally, even when they're meant that way. It's the same sort of process for coming to grips with infidelity where you have to learn that the affair wasn't about you (but, oh, fuck yes, it absolutely is about you).
Not sure if this is helping, because it's all pretty high level stuff. If you want to have a discussion about actual things to do: strategies, preventative measures, day-to-day management shit, we can do that, too. I'm a little hesitant to go there because I've only ever been married to one bipolar wife, so I'm not sure I can generalize what's (more or less) worked for us vs. what will work with your wife.