The correct answers are We have been watching the suspect's house since midnight and We have identified three new accomplices so far.

Present Perfect Continuous is used for ongoing actions that started in the past and are still happening (like watching the house).

Present Perfect Simple is used when we focus on the result or a specific quantity of a completed action (like identifying three accomplices).

"Know" is a stative verb, so it cannot be used in the continuous form (it should be have known).