1) If a player rolls a six, but is assisted up to a 7, do they still mark XP?
No. The roll result is no longer a miss (6-).
2) I'm still a bit unclear about range and assigning negatives. For example:
Bob the fighter is locked into melee with a nasty orc. He swings his broadsword and misses and the orc slips in past his guard into close range, bull rushing him up against the dungeon wall. Bob, what do you do?
a) I skewer the brute with my trusty sword! But at this range, it's awkward; do I just arbitrarily say he can't, or should there be a -1 or something?
"Cool, Bob, but how do you run him through when he's up close and in your face and about to stabby stab you in the gut with his 6-inch knife?"
b) I grab my sword with both hands and smash the pommel into its head! So... is that just standard hack'n'slash, doing normal damage? Doesn't that make the range tags pretty much pointless, since they can always be circumvented by the fiction? Or should/can I say that the damage is halved or something, using the weapon in that way?
Couple ways you could deal with this, and there are a few principles and your agenda to guide you.
Be a fan of the characters tells you to let it be a normal H&S, so does
Think Dangerous.
Fill their lives with adventure and
begin and end with the fiction might tell you to do reduced damage. And you might want to
ask questions and use the answers before you decide.
Is the orc wearing a helmet? Have you established that orcs are big, tough, I-don't-give-a-fuck types? Maybe the move just does stun damage, enough make the orc stagger back and get back to a more optimal range. Or maybe it does half damage. I could go either way, and my answer would be informed by who the PC is. I'm much more likely to let the figher or paladin get away with dealing damage in a suboptimal situation than the bard. Fighters and paladins are badasses.
c) Holding my sword in one hand, I bash my gauntleted fist into its face: normal hack and slash? Defy Danger if the orc is wielding a dagger? Any negatives or anything unless the player has fictionally created a backstory of fisticuffs? Or would the punch just stun the orc?
That sounds like H&S to me, with stun damage as the result. Again, might depend on who's doing the punching and the nature of the foe. I'd probably go with stun damage. "BAM! The orc staggers back a few paces, shaking it's head and spitting blood. What do you do?"
Of course, if the orc was
already trying to knife the PC in the gut (i.e. you'd established that he was doing so, probably as part of the soft move that put him into close quarters), I might ask the player what he was doing about that knife. If he ignored it, I'd deal damage from the knife and
then let the PC H&S to punch the orc in the face.
d) I bodycheck the orc, shoving it back, and the skewer him with my blade! Defy danger to push it back then hack and slash, or is this combining two Moves into one?
I'd probably go with Defy Danger (+Str) and then (if successful) a H&S. The range tags are what make me think that. DD to address the imminent danger of an orc in your grill, making it possible for you to attack with your sword (H&S).
Compare that to "The orc lunges at you with his rusty sword, like right at your throat. What do you?" "I parry the thrust with a bind and riposte!" "Cool, roll to H&S!" You could argue that the PC is Defying Danger or Defending and then Hacking & Slashing, but I think almost every GM would call that just a straight H&S.