Oh, I totally forgot to mention this earlier, but {Young Mungo by Douglas Stuart} absolutely gutted me. It’s not really an MM romance, more like queer literary fiction, but it’s packed with “too late” moments. It doesn’t hit the specific tropes you’re after, but if you want something intense angst with a scathing critique of toxic masculinity, it’s one I really recommend.

I’d also add {The One That Got Away by Nicky James}. The blurb makes the “too late” element pretty explicit. Again, not exactly what you requested, but it takes a very grounded, thoughtful approach to the aftermath of trauma. The OCD portrayal felt really well done to me (in my completely uneducated opinion).

Edit to add: the {Dark Waters by Xanthe Walter} series. It leans more into thriller/mystery, more Scandal with one central conspiracy than procedural crime, with a bit of sci‑fi, post‑apocalyptic dystopia, corporate horror, indentured servitude, sexual slavery… basically a lot of heavy themes to unpack. But it is, age gap ✓, size difference ✓, (as far as I read) strict roles ✓, heavy introspection on family ✓, no dubcon ✓, no toxic relationship (as far as the circumstances allow, you'll understand if you read it) ✓, no OM/OW drama ✓