Also possible he was told he would be “participating in a training excersize”. Someone in the SS had to open the way for this, and might have been hoping that the irregularities would be lost in the confusion after a successful assassination.
Yes, that’s another possibility.
As calm as he was and telling his employer he’d be back on Sunday, as well as having two vehicles there and the explosives, it seems like he was thinking he would survive this.
To be truthful, I think the slow leaks and contradictions are to get us to miss the forest for all the trees.