3. One time, my friend was in combat. I played "Curse! Change Sex" on him to -5 his next combat. However, he objected by saying it would apply to his next combat and not his current combat. When does it actually apply?
It applies to the curent combat sinse the first fight after sex-change is that fight
4. If Player B plays a curse like "Curse! Lose 1 Big Item" on player A, who gets to choose which item is discarded assuming there are two Big items on player A?
The player A chose which item will be discard. BTW You can't have more than one big item "in play" (All Items on the table are "in Play" -normal or turned sideways-,those that you have turned sideways is "carried" and the ones that you have normal are "in use"). Only Dwarfs can have as many big items as they want in play.
5. When can cards be put sideways? If I could put down cards sideways endlessly, why does charity exist?
You can't put Cards sideways. You can put only Items sideways. By this point the items are consider as "carried". All Items has a value in gold in the right corner or "no value" label. all other cards are not consider items so you can't put them "in play". You can have as many Items as you want exept for "big" items that you can only have one "in play", "carried" or "In use"