ADHD Marriage - Doomed?

I've been with my boyfriend for a year and a half now, and about six months ago he was diagnosed with ADHD and placed on an Adderall regimen. He's been reluctant to talk about it, so I've only just now gotten around to researching. But now that I'm looking into it I'm finding all kinds of horror stories about partners becoming completely uninterested after marriage ends the "hyperfocus courtship," partners having emotional or sexual affairs when they meet someone new and shiny, or partners ignoring the children. Since we're on the cusp of getting married, I'm feeling like my happiness with him thus far has a death sentence and I'm hugely panicked. I love him, but I can't face a future where he will stop loving me.

So I really want to know: Do these things only happen when ADHD people are undiagnosed/untreated? Are they inevitable? My boyfriend has had issues with hoarding, not being able to get work done, and sometimes I feel like he's fixated on other women, but these things have lessened since he's started his treatment. I need to know if I'm doomed and need to cut out now, or if there's any hope he'll be better in the future.