the simple way i use if i want a long movie/dvd split to 2 DVDs is:
insert dvd. launch dvdshrink. choose open disk. choose the dvd location from the dropdown menu/ok. click reauthor. drag main movie title across to the left pane/dvd structure window. click on the set start/end frame button [two arrows facing opposite directions]. now, if the movie has, say, 30 chapters then leave start at chapter 1 [default], but on the end chapter, the dropdown BELOW, set it to 15/ok. now click backup, set your options to save as ISO or burn or whatever. now you go back and do the same operation, but you start at chapeter 16 and end at chapter 30. this way you have split the whole movie to 2 DVDs . Done.