What are the expected tips in these places?  Are they the same as they used to be in D.C. before the AMPs (or most of them) were closed?

I would stay away from amps in VA.  I was told by an amp worker you will not get the service you expect to when in DC. So you end up paying close to $$ for a hand shake.  I can do that better myself. If amps are what you want you will have to stick with DC for now.  Although that scene isn't what it use to be.