Can anyone help me out on how to find the second lever to get into the mine?
Check out the anti-vampire camp in the SW corner of the map. You need to progress quests there and hug people after completing them. Someone fixes the boat for you out of gratitude. Someone on that island has the lever.
More detail:
It's the people looking for somewhere to perform. Play their tape to the music store owner. Take the card back to the band members. After the performance, talk to the dude under the truck for the boat fix. The guy on the island has the second lever. You need to get that picture in the house to his brother back in town.