So sorry about the loss of your dad and so sorry that also its not really possible to answer your question about how he was those days after you saw him, except to say in my experience it is likely he would have been just how he was when you left if he was already unconscious then, but that doesnt mean he was totally unaware of your prescence at the time subconsciousley,and appreciated that and i think thats what matters most because it is about your relationship with him over the years of both your lives, rather than just those last three days of his.
With your step mum it is also really difficult to know - whatever your relationship with her was like before this happened i think - again speaking from experience, of caring for some-one in that way and caring for him at home in particular would have been exhausting both mentally and physically, and how we deal with that is different from each other but maybe she lashed out as a result - potentially pushed by the friend, who may well have vey fixed views about how she perceives people should act at times like this based on a time in the past when famillys were just around the corner and not 150 miles away, it isnt your fault that those times have changed ot that her views have not, Again the "everyone" who had visited may simply have been appeasing her, because you are not going to argue with a soon to be widow, but it doesnt necessarilly mean you agree with her or dont understand the difficulty that was there for you but not want to say so at the time you make that visit.
You dont say whether or not there has been a funeral or if you went too it, if so what was her reaction to you then or has she cut you off since then,but if you are still facing that and unsure of your part in it, then its important to remember it is about him and his life, not her or her friends opinions and base your decisions on that, but if she arranged it without your input then perhaps parts of it wont be something you agree with,or you think of as being about him - so perhaps you can walk away from that and think about doing something else later as your memorial too him but also somewhere you can grieve nearer to home - maybe plant a tree rather than a second headstone - or take your familly to visit somewhere you remeber him taking you as a child that was a happy memory.
Whether your relationship with her is now brocken or was always brocken - again i dont know but while i dont condone her behaving like that it is important to see there may well have been a cause behind it and lashing out like that was the result.