About "Memento" (the movie), is Teddy's revelation the "truth"? (SPOILERS ahead)?

Question

Repeat: SPOILERS BEYOND THIS POINT.

My interpretation of the "real" story was that what Teddy confessed to Lenny was the truth. I.e. the two intruders did rape Lenny’s wife, but she survived the assault. During the scuffle, Lenny conked his head and lost his ability form new memories. His wife (revealed by Teddy to be diabetic), couldn’t handle (didn’t want to believe) Leonard’s condition. So she tested him by repeatedly asking for him to give her her shots. He complied and ended up killing her. Of course, he doesn’t remember this, with his condition.

What I don’t get is: One, why do critics repeatedly refer to his wife’s “killing” by the intruders in reviews, when according to Teddy, she survived?

Two, how can Leonard alter his (long-term) memory of Sammy (giving him a fictional diabetic wife) as a reaction to killing his wife, when he can’t remember killing his wife? Doesn't he have to remember the trauma of killing her to have the impetus to alter his memory of Sammy?

Answer 1

If Teddy is telling the truth and Lenny did kill his wife, wouldn't he be in a skilled nursing facility or something to that effect? Did you notice that flashback where Sammy's face turns into Lenny's for a split second?

Also, Lenny has the ability to remember things from the past, he just can't form new memories, so he probably remembers that Sammy had a condition similar to his. Maybe that's why he confuses them.