I have to put in a sewer line. It will run about 75 feet from house to sewer line hook up the county put in it's about 4 and a half feet deep. How much should it drop? 1/4 " per foot or 1/8" per foot? How deep should the pipe be what size pipe 3in or 4in? Have cinder block house, how do you cut a hole for the pipe without knocking the whole block out? I have done many repairs to a home but NEVER anything like this.

Your drop should be no less than 1/4" per foot but the lay of the land may cause that to be at a greater slope. Less than 1/4" per foot will not drain properly. I would use a 4" PVC drain and knocking a hole is no big deal. Where to exit may depend on how well you can calculate that 1/4" drop. You may need to make your hole high on the wall , but still below grade, to get your slope. A cement block has two comparts so use a hammer to smash one side or the other of a block, patch cement around the pipe once you are done.