You'll need to hire a defense attorney or request a court appointed attorney to defend you in the criminal case.  You're not going to have much luck with the other matters as far as a civil suit-- for various reasons and exceptions.  For example, grand jury proceedings are confidential and they are not required to tell you when the grand jury is going to convene.  Second, the change in the castle doctrine is still very new with limited interpretations-- but many interpretations only extend to your home, and don't allow you to chase someone down in your yard.  If interpreation is later rejected, then the agency will have governmental immunity -- which means you can't sue them.  Third, they can search a crime scene without a warrant.  Warrants are always a better practice, but are not required at certain times-- investigating a crime scene is one of them.  If the search was illegal, the only remedy would be the exclusion of any evidence found at your trial.  All of the actions you described are fairly typical becuase they are in the course and scope of their powers and duties.  If they had gone beyond their scope, like beating you senseless, then you would have a civil suit.  Right now, your best bet is to get an attorney to help you on the criminal end.