I have just read this thread for the first time, Disco.
I’m sorry you are dealing with so much now.
All it has been said are good advise. I particularly wanted to stress on not denying your feelings, let yourself being sad or whatever you may feel. Thoughts of sadness are going to appear in your head, don’t deny them but let them pass by accepting without torturing yourself with them. Try to focus on your routine or something your energy let you do to distract yourself. This way, you will mourn little by little each day.

Those moments where you can cope with the pain, write your emotions or whatever you need to write on a journal and open yourself to your son or your husband. Also, be ready when your husband needs to talk about his best friend’s loss.

This is how I cope with loss. Especially, allowing myself to do what I need at a time.
I’ve slept with my doggie’s blanket by me for two months. After three months of his passing I still haven’t been able to see one video of him.
When my dad passed away, it took me six months to open a box of his movies DVDs to place them on my shelf. It takes time and patience. And you have to be very nice with yourself. Don’t feel bad for not being able to have enough energy. Life will not be the same but it will be a new version that may be positive, too. With time.
Even November rain passes by.