Morning OP. One day and hour at a time. What you are going through is shock and grief, be gentle with yourself.
Firstly have tea, or coffee and if work aren't providing lunch, make yourself a sandwich to take. Small practical things will help you to plod on, and eating is important.
If you feel you must go to work (and a distraction can be good) then tell the course tutor privately that you've got some distressing personal stuff going on so are not on top form.
I'd definitely ask him to move out so that you have a safe space to live in.
I'd cancel the overnight stay - use the same reasoning as for the course. You don't have to give details. You may want to say 'I'm splitting up with my husband '. People will understand.
Do you have an employee assistance programme at work ? They are good and confidential and should offer immediate help re legal and or counselling. Alternatively if you have private medical they can offer mental health support too.
Don't make any decisions about police or holidays yet. Give yourself a couple of days. Get him out of the house first to give you space to think and plan.
If you have a trusted friend then call them now. This is the time when dear friends step up. You'd do the same for them, so it's OK for you to ask for their help. You need it.
One step at a time. You can do this.