Gabe wasn't against anyone and you know it. In fact he was solidly with John when it came to winning challenges, providing food and building the shelter. He was willing to be used. That is the perfect ally.
Comparing this situation to what Rob faced in Redemption island misses a key difference: John had a post swap tribe, meaning he had 3 easy targets to boot. "The easiest way to guarantee a Rotu majority in the new Rotu" was by booting a oldMara'amu. Can't be easier than that!
Also, about Morono's decision to boot Matt: Do not confuse a huge gamble with sound strategy. It worked in RI for Rob but his taste for gambling is why he won only on his fourth try.
"If John would have recruited Kathy into a F5 deal..."
Besides Rob and Sean, Kathy was the last person John could have manipulated. He needed Paschal and Neleh, thought he had them but they had been worried since the Gabe boot.