Why not just select the proper sensor for your application, a true differential pressure sensor with the pressure range you require. Such a sensor will have two pressure measurement ports, a high side and a low side that you route (perhaps using plastic tubing) to the two points you wish to measure across. This will give you both the range you need with the best resolution possible. The attached product sheet shows that they are available and I'm sure there are other manufactures. Be sure you check that they can handle to medium and temperature you will be using, many of the lower cost sensors will only work in dry air medium.