Continuity mistake: In the kitchen, Billy's mom shields her face with a table. A frame later it's at waist level. (00:54:50)
Sacha
Continuity mistake: When Bill is in the bar drawing a cartoon of Mrs Deagle, the amount of popcorn on the table increases between shots.
Sacha Continuity mistake: After Gizmo poops, there's a close-up on Billy's stunned face, perfectly lit. A frame later, from a different angle, the face is in shadows.
Sacha Continuity mistake: Both the scene of Billy, Pete, and the science teacher looking at the gremlin cocoon, and later when Pete is in class watching the science film, occur on the same day, yet Pete is wearing different clothes.
Continuity mistake: When Billy smashes the Candy store window the amount of stuff behind the glass changes between shots. (01:27:50)
Sacha 
Chosen answer: The precise cut-off point is never stated - I've generally assumed that the embargo on feeding finishes once the sun comes up.
Tailkinker