1. If the Dervish wins a battle and chooses to move a number of spaces equal to the strength of the enemy, are all other cards drawn on the original space no longer available for encountering? In other words, would a successful battle prevent the Dervish from encountering a spirit, place, or object drawn in the same space as the strength enemy?

2. Is it conceivable that the Dervish could have multiple successive turns if he continues to draw enemies with which he could battle and he wins and then moves to another space and encounters yet another enemy to battle? (While highly unlikely, it seems the Dervish could seem like he was having an unending turn, at least until he ran out of enemies to battle or lost.)

1. Yep

2. I don't see why not unless it says once per turn?

1. If the Dervish wins a battle and chooses to move a number of spaces equal to the strength of the enemy, are all other cards drawn on the original space no longer available for encountering? In other words, would a successful battle prevent the Dervish from encountering a spirit, place, or object drawn in the same space as the strength enemy?

Yes, you need to give up encountering the other cards to continue your turn. Using the Dervish ability isn't always be the best option, even though it's great to avoid nasty Craft Enemies, Strangers, Places and fireland tokens.

2. Is it conceivable that the Dervish could have multiple successive turns if he continues to draw enemies with which he could battle and he wins and then moves to another space and encounters yet another enemy to battle? (While highly unlikely, it seems the Dervish could seem like he was having an unending turn, at least until he ran out of enemies to battle or lost.)

The ability can be used many times in the same turn. In the Dungeon a Dervish in good shape can often stretch his turns for long, but if he kills many Strength Enemies together the "whirling" move might be exceedingly long to actually take it.

I can see the drawback that keeps this from being OP. The Dervish misses whatever else was drawn and could leave behind a board littered with cards