I wouldn’t.

Just a backup in advance of the detumblring
I wouldn’t.

Well, the Mastership of Ships would seem to be a logical reward.
Just give him a giant tree-club, and that shield wall could have been broken easily…
Well, it got the Baratheons enough prestige to be acclaimed Kings of Westeros by the Tullys, Arryns, Starks, and Lannisters…
Yes and yes.
It’s more that the time gap between the Green Fork and his full-scale betrayal at the Red Wedding is unusually long. During the Wars of the Roses, there were quite a few people who betrayed their own side during a battle, but usually they defected right afterwards. To quote myself:
Probably the narrow area between the Firth of Forth and the Firth of Clyde.
She wrote to her mother to give her an excuse to tell Robb she was pregnant, to make her death that more horrific.
As to why Talisa is more invented, it’s more that Talisa exists only to die. Jeyne has a specific backstory that is a significant part of the Red Wedding – she’s a Westerling, which creates a Romeo and Juliet thing b/c she’s a Lannister bannerwoman, her ancient but poor house maximally pisses off Walder Frey, her mother being Sybell Spicer the granddaughter of Maggy the Frog is linked to Tywin’s plotting to trap Robb at the Twins – and significantly, she survives the Red Wedding. There is more to her story than dying at Robb’s side.
The clans had been growing bolder because Lysa had called all of the knights of the Vale to the Eyrie to defend her, and forbidden them to go on patrols or punitive expeditions to keep the clans down.
My thought is that the writers and showrunners didn’t think it mattered, b/c she was invented in order to be killed.