Welcome! I hope you found/received some suggestions. While I’ve ridden that way to Silver Spring a few times, I haven’t done it frequently, or to commute. Others here may be able to offer specific suggestions on routes.
Regarding your question about the trail – the MBT gets a lot of use. Trails in general are getting more use during the pandemic. You are likely to encounter other users mid-afternoon. The number of users will likely go down in the winter, but I’d still anticipate encountering some people during your ride.
I’d also offer some general suggestions:
– The Strava heatmap can be a useful tool to see which roads people are riding on and for planning routes: https://www.strava.com/heatmap#14.55/-77.01504/38.96093/hot/all
– Google maps street view can be helpful to gauge what a street might be like .
– Once you think you’ve found a route, test it a couple of times on the weekend (or a non-work day), carrying whatever you plan to take with you on your commute, to give yourself a lower-stress opportunity to get turned around a bit and explore.