Anyone who's been hospitalized and unconscious for three weeks would need to be hooked up to an IV and catheter. Nurse Gallagher's comment about having "had a look" at David's privates shouldn't have invited criticism from the others, as it'd be among the nurses' daily duties to check that the catheter remains in place.
Looking at his penis is part of her job. Gossiping about it to other nurses afterwards isn't.
One problem at the end: when the firing squad kills werewolf David, Alex was standing right in front of them when they did. How did she not get hit too?
She's standing still and they're using rifles with telescopic sights. It also appears that only the officers who can actually see the wolf fire, as there are only 3 or 4 shots.
Come to think of it.... In the final scene, how does Alex suddenly know that the werewolf cornered by the police was David? For all everyone else knew, it was just a giant, bloodthirsty mad dog. Not to mention, throughout the movie until that point, she didn't even believe in David's ramblings about being a werewolf.
Jack said his spirit was trapped in limbo until the werewolf that killed him's bloodline was severed...so back to the dawn of time no other werewolf in David's bloodline had taken a life before Jack? Shouldn't there be an army of ghouls?
Possibly there are, but David just can't see the ones whose deaths he didn't personally cause or witness. Jack does imply he's been talking to other dead people even before David's first rampage.
Where was David's family in all of this? The poor guy spends three weeks in the hospital and there's never any indication that his parents came to check up on him. The only people who came from the States was Jack's family. Even after David is discharged his family doesn't try to reach him, and when he later calls home his sibling seems less than interested in talking to him. Why wouldn't they try to check up on him when he was unconscious for three weeks and his best friend had died?
At best, it's mentioned that his family made arrangements to wire money to the hospital to pay for his treatment. But yeah, that's pretty much it.