I'm going to be real with you because I've been there, both as the girlfriend and the person being accused of heinous things online (I'm also someone with a low level public profile).

Everyone who says "twitter is not real life" is full of shit. Is losing your job as a consequence of what people say online "not real life"? Is losing friends "not real life"? Is becoming suicidal "real life" enough for you? Honestly, some of you are very immature and fucking stupid.

If you have a public profile even in a niche area, you're going to have to contend with being scarred forever, and all of your relationships, save those with your family, are going to change. Some days you'll feel fine, full of righteous indignation, and stronger for having survived. Some days, you're going to feel suicidal. The dynamics of every relationship in your life will change, because you will start sorting people into categories: those who stood up for you/stood by you, those who bailed on you, those who joined in with the accusers, those who were totally silent over fear that they'll be smeared too, but who expect to still enjoy your friendship. This extends to the future as well. Every time you make a new friend or meet a new professional contact you will wonder: "how long until they google me and find out, and will they stay in my life after they know? Will they believe it?" I've learned to keep everyone at arm's length, years later.

Does your boyfriend drink or do drugs? It sounds like he does. I recommend getting into recovery, and not just because alcohol is a depressant and drinking is an unhealthy coping mechanism. People are remarkably forgiving when it comes to anyone who's overcome addictions, and many are even willing to write off past behavior. Of course, people are far less lenient about this now, post-metoo, but I can tell you that being a recovered alcoholic/addict will buy you some support and give you back some much-needed self-respect. Other addicts are also tremendously helpful for dealing with feelings like shame.

Get a therapist. I was able to reframe my situation as the result of involvement in contentious political issues, in which character assassination is not uncommon I'm not sure how this would work with false rape accusations, but you can rest assured that your boyfriend is not alone. There are many other guys going through this.

Anyway, it's horrible and humiliating, yet most people do move on and forget. I'm obviously biased here but now when I see someone being "cancelled" on Twitter, the person doing the multiple tweet-accusation thread comes across almost as bad as the accused. Even if the reputation of the accused is damaged in my eyes, and lead me to somewhat keep my distance, I generally also note to keep my distance from the messy canceller person. This is probably the best you can hope for in the short term.