The word "now" is used here to mark the change from the lists of descendants to background information about Reuben. (See: [[rc://en/ta/man/jit/writing-background]])
This can be stated in active form. Alternate translation: "but Israel gave Reuben's birthright to the sons of Joseph, another of Israel's sons" (See: [[rc://en/ta/man/jit/figs-activepassive]])
This is a polite way to speak about Reuben sleeping with his father's secondary wife. The couch is the place where a man and his wife would have slept together. (See: [[rc://en/ta/man/jit/figs-euphemism]] and [[rc://en/ta/man/jit/figs-metonymy]])
This can be stated in active form. The word "recorded" carries the idea of a written record, so if your language has such a word, you may want to use it here. Alternate translation: "the family history does not list Reuben as the oldest son" (See: [[rc://en/ta/man/jit/figs-activepassive]])