How to support partner? (2nd parent dying)

[Manchestermummax3]

I'm in the very fortunate position that both my parents & even my grandparents are still alive.
DH father died before we met.
Now his mother is dying, literally just found out. Although elderly, it's a total shock, no indication of this happening anytime soon.
How do I help/support him? I don't want to be overbearing but I don't want to seem like I'm not doing enough either. I don't know how I'm supposed to help?!
If its any reverence, he has a brother but other than that not much else. Other relatives live 100s of miles away or other countries.
He's the type that stereotypically is the male emotionally stunted type, he's not a big talker. So far he's just gone on autopilot doing DIY, cleaning the car, doing a food shop.
Hes supposed to be on a works night out this weekend & I know it's not a good idea... he will drink himself stupid.
Do I just let him work it out his way & just be there to pick up the pieces afterwards?

I'm not sure from your post how long she has left?
Nor how far she lives from you ?

If possible, I would be gently encouraging him to spend time with her now - both from the pov of view of not wishing he had done so when it was too late, but also from the very practical side of finding out what her wishes are regarding things like funerals, but also helping her get paperwork in order.