Hello, and thank you for these questions!
In fact, is there an entire score at all?
No! You only keep the lowest single die of 3d6 as your de facto modifier. There's no 3-18 "score" in the traditional sense. This was inspired by another micro-game called Knave.
[Combat ends], what does that mean if people are up still?
It means you narrate the outcome. We've had anything from the opponents surrendering to the player characters escaping to them getting bundled up in a prison cell. The intention of the mechanic is to keep the pace really high and to mimic the kind of storytelling that classic S&S authors stuck to, as a legacy of the pulp era.
What if one wishes to use Sorcery outside a combat situation?
When we've played it, using Sorcery can be done as a scene of its own. The player would roll for actions and then the DM/GM would roll for actions as well, representing the demon being contacted.
In fact, this kind of preparatory sorcery makes it a lot more predictable for players, since you can then have your pacts done in advance and you will know what you have when there is a fight or other situation.