Another coloured hair blonde here.
Perfect condition for years until hairdresser wrecked it with over bleaching.
I hate to say that once it wrecked, it's wrecked. I tried to keep mine as long as possible, but it just kept breaking, even hair that wasn't so badly damaged, because the slip ends go further up and it will break eventually. So it was miserable because I didn't have it coloured badly again, but for nearly a year it kept breaking. Once enough damage is done, it's done.
I'm not chopping off as much as I can stand, as often as possible.
Coconut oil treatment, yes, Biotin will make new hair grow through more quickly and make it stronger.
I hear good things about olaplaex too, although I haven't tried.
There's a difference between damaged, which is unavoidable with colour or heat, but can be cared for with treatments and good haircare, and broken, which there's nothing you can do about.
I hate it too, I'm really frustrated with mine at the moment because I've been messing around for an extra year with it continuing to break and look worse rather than better.
If it is literally breaking as you put a brush through it, cutting some off is a good idea. Conditioner won't help that, no treatment in the world can deal with that.
Sorry, completely feel your pain here.