So glad you got through your first morning back at work LoserNoMore for the next while all 'first' things (post-split, IYSWIM) are tough!
I remember finding so many things really difficult .... it didn't necessarily have to be things that we had done and enjoyed together (it just as easily could have been a school meeting or taking kids to the dentist, things I'd often done myself anyway).
I think it was the fact that the last time I had done that thing (be it go to work, or the dentist, or whatever) I had been part of a couple and life had felt normal.
Suddenly here was everyone carrying on as usual (which it was for them) and I felt not-quite-of-this-planet!
Anyway, in a kind of backwards way I am glad your boss was off, not because I don't think you should change your hours if that's what you want, but because this is a period of so many changes for you, it gives you another day or so to decide exactly what you want from your changed hours. Might as well ask for everything in one go!!! I hope they are co-operative and give you the changes you need.
Rotten not to be able to take some time off, just now. Have you got some childcare in place for the rest of the holidays, or was it your H who was going to be covering your working hours? (Ohhh, I hope not)