why the tunnels under the house make no sense
How did people not know about them? Someone had to build it. Maybe they were there from previous owners. Or Mr. and Mrs. Myers were home improvement enthusiasts. Or hired multiple workers and kept switching them out.
Also. The very existence of those tunnels suggest: A: Mr. and Mrs. Myers were crazy abusive toward Michael. 2: They, like Loomis, knew they were dealing with evil, and tried to keep it locked away. Or a combination of both. But none of those allow for as to why he would've been allowed to just wander around in the opening of the original.