On an emotional support side Manda, make yourself available to your Mum, perhaps by ringing her weekly or fortnightly depending on the cost. If she can't use the internet tell her about this site and that if she has any questions you can post them here for her. Also be aware that your mum may feel like she can't cope sometimes, that your mum may need to consider putting your father in a home so that he can get the care he needs. I'd say don't push her to make such decisions but be a sounding board for her, let her know that you support any decisions she makes and that you will be there for her if she wants to cry, if she wants to be angry about your Dad's behaviours (this is normal) and if she just wants to chat to another adult for a bit. Sometimes if I disagree with how my mum is dealing with something to do with Dad, I just tell her how I see it, but point out that I am aware that she knows the situation better than me, what she can cope with, what she knows Dad can handle and I will support whatever she decides regardless of my viewpoint. Remind her that you are an adult now and that she shouldn't be putting it all on herself and trying to protect her daughter, you are there for her whenever she needs it, even if you can't be in the same country.
Lastly, you too need to look after yourself Manda, know how much help you can be, as a daughter I have found losing my father very distressing and sometimes it has been harder when there is great distance between us, because you suffer the guilt of wondering if you should do more but at the same time know it would make little difference if you were closer, and each time you do see him you are extremely shocked by the change. For this I would recommend posting on this site when ever it gets too much and you need to rant and rave. Don't think just because you are so far away doesn't give you the right to be in pain and hurting.