I have sensed mana on purpose, prior to being an angel. The flow of its predecessor - Aer - upon my world was not stable, and following it when it was trouble would lead to problems that needed to be fixed. I had more freedom of movement than others who would fix such things, and thus I would go.

[ So no, being an angel didn't make him be able to sense mana. ]

... I sense in greater detail, currently. A wider area, at the very least.

[ It just made him better at it. ]