1. When you Sacrifice explorers for a mission, do they come off the ship or can they come off your race card? If they came off the ship do they go to your race card or the pool? Thematically it made the most sense for them to come off the ship and go to the pool, but that wasn't explicit.
Come off the ship to the pool. (So you were correct).
2. How do you resolve a tie in DP when the game ends? We used explorers on the ship as the first tie breaker, with trained explorers on the race card as the second.
The only tiebreaker is points from room control. If there is a tie there also (so you have the same number of points from missions and rooms) you share victory.
Hope this helps.
Cheers and happy new year,