1. It appears that the police is compromised in this case.
2. You better file a writ petition of Mandamus in high court against police inaction so the court direct the Police for necessary action including submission of charge sheet. The court can not ask the police to arrest the culrpits but can direct them to be more active.
3. Yes the police can submit charge sheet even without arresting the accused persons. If they do so then the accused persons would be shown as absconder in the charge sheet. The the Magistrate will issue fresh warrant against them including lookout notice.