The Dwerge, or correctly Dwergi (Old English dweorg, Old Norse dvergr), are small humanoid creatures with sharp teeth that act as minions or servants to Dracula. In German folklore, where this character is borrowed from, they are actually dwarves.
Van Helsing clearly states that he only kills monsters/creatures of evil. Frankenstein's Monster was not evil. Therefore he felt that he could not kill him even though, on several occasions, the monster asked him to.
During the final battle, Van Helsing kills Dracula when in his vampiric form. As Anna bursts into the room with the werewolf antidote, it is assumed that Van Helsing is on a rampage and leaps onto her probably causing her to die in the impact. She managed to inject him with the antidote before she died, causing him to transform back into a human and be cured. Van Hesling and Carl hold a cremation for her by the sea where she is at peace and with her family in heaven.