The Kid was definitely part of at least one ambush/assassination. That was the killing of sheriff Brady in Lincoln, as well as his deputy, George Hindmann. The Kid was one of a party of Regulators who ambushed them from behind a stucco wall as they walked along Lincoln's one street. The killing of two of Tunstill's killers, Bill Morton and Frank Baker may also have been premeditated. The Kid was a part of that as well.
Garrett and the Kid did know each other, but their acquaintance has likely been made too much of. And the idea that Garrett let the Kid go, faking his death or substituting another body, is just another conspiracy theory too many people give credit to. That's really what's behind this pardon attempt.
That Lincoln County jail was actually the Murphy/Dolan store. Their business went bankrupt and the county took over the building. Garrett had his office upstairs on the 2nd floor along with a room for prisoners and a weapons room. The Kid was kept in Garrett's office, an upfront attempt to prevent him mingling with the other prisoners. Garrett was away on county business the day the Kid escaped by killing his two jailers. There's also nothing in the idea that Garrett had anything to do with that. What sheriff would be involved with a prisoner scheduled for execution, allowing his escape when he's as desperate and dangerous as the Kid was? That's just plain goofy thinking.
The Tunstill store is still there as well. It's reputedly exactly as it was at the time of the Lincoln County War, and a major attraction for the City today.
Billy the Kid and the Regulators
The foundation of the cafe is still there.
Why would the townsfolk allow Billy to sit on the front porch and wait for help in getting his cuffs off? And who helped him? And why would they allow him to ride out of town wistleing a tune? He had just gunned down two deputies. Was everyone in town that afraid of him?
No doubt about it that Garrett lay in waiting for Billy. From what I’ve read about his prowess with a gun you can’t blame him. Maybe that answers my questions above.