Yes, it’s OK to agree to the divorce that she asked for. Trying to care for someone without sufficient help can be overwhelming and all-consuming. And younger people don’t have resources or models for when you need full time (or near full time) care. Giving up all of your hobbies and being solely responsible for someone else is not healthy. But we rarely talk about care-giver health unless it’s to say stuff like “Well he’s been by her side from the start.” or “He’s just living his life not thinking about her at all” – there’s almost no middle ground. The healthiest of care givers get some kind of respite and maintain some of their social activities if only to be reminded that life continues.
So yes, you’re allowed to feel that weird combination of grief and relief.