i would like some explanaitions about the ending(spoilers alittle)

could someone please tell me whats the ending all about
was he making a movie for real all this time and the end was just to clear up the story or is there something more to it

and why were there people when the women got crusefied???
and when he shoot them in the head that was not real to???
and when he said he failed and his holding wendy what does he mean by that???
was he supposed to call on satan, which he them told his son to snuff boris???

am looking forward to some anwsers because this mopvie is the most confussing i have ever seen :-)

edit2:i have saw the ending again and now i am even more confused
i think u heard that andy came to boris for a cheqe (money) for his playing and wendy wasnt really his girlfriend and all of that was played also and she was for real borises wife and he was playing that his wife has died???

i odnt want to confuss anybody just want the truth please :-)