BW,
I used to commute regularly through both Henderson Hall and Ft Meyer, essentially a short-cut between 14th St Br and Clarendon–and that was around and after 9-11 so security was heightened. I had civilian DoD ID, and I was often asked for it when entering either reservation. I’m sure DoD affiliation helped. I recommend make a telephone or written request to the post Provost or transportation office. At least you’ll get more information, or maybe even a pass.
If all else fails, consider this route to avoid pass-thru. I also did this route regularly before discovering I could cut through the posts. Surprisingly, Washington Bvd is not so bad! Shoulders are 15′ and it is well graded (former rail/trolley line). Have to be aware and use great caution crossing entrance exit ramps. More than a few times (heading towards DC) slightly downhill, I picked up a dump truck at the Pershing stoplight on Wash Blvd, and drafted to Rt 50 or even Columbia Pike (once I think I got close to 50 mph!) Though I don’t recommend drafting dump trucks on Wash Blvd,.. but it was fun, (though very foolhardy)
Dave