@Hedjwitch When DH died I had already given up my permanent post because it became impossible to cope with the demands of my job and DH had suffered - he scalded himself at home whilst I was working late. (An unsympathetic boss kept heaping more and more work onto me. With hindsight, I should have sued for constructive dismissal. He was eventually suspended for bullying.)
What I will say is that I missed the structure of work. I always found work to be a good distraction from other problems, but maybe I'm weird that way.
I went back to supply teaching after DH died. I'm sorry - I can't remember how long I waited, but it can't have been that long because you're removed from the books if you haven't worked for 6 months.
I only did it part-time, I should add. It did help, but it would have been much better for me if I'd still been in my original permanent post. (I was full-time and unwillingly dropped to a 4 day wk before quitting completely.)
One of the times I was on supply, I found myself teaching in DH's old classroom. (We met at work - not the school where I had my final permanent post.) I got a bit emotional, but held myself together and was okay.
You'll be returning to your normal place of work and the familiarity might help. The fact that you have a supportive boss and nice work environment sounds positive to me.
I know that I would rather have been at work than in the house on my own all day. In the interest of full disclosure, I've no children and no siblings, so was very much on my own. It might be different for you, but since you have a good boss, maybe you could try it and see how it goes.
I agree that the longer you wait, the harder it might be?