Sorry to hear about the crazy driver. I think you're better off going to a car seat check station to get a great fit on your seat and to get some good advice on seat placement. Here is a link to where you can find one locally (we are in Northern CA and made an appt with our local CHP station)
http://www.nhtsa.gov/cps/CPSFitting/Index.cfm
Otherwise the best online resource is through car seat . org. Be sure when posting your questions to include the make model year of your mini van and your car seat. That will help give them an idea of how to answer your questions.
good luck