Minor point - Fredericksburg is 55 miles from the middle of DC. Frederick is 50, and Hagerstown is 70. Let me guess, you live in Montgomery County?
No, I actually live in Virginia. But on weekends - the only realistic time for me to make games - there is no comparison at all between 270/70 and 95.
Do any other MLB teams outright own a minor league affiliate?
Yes, there are a number of MiLB teams owned by their major league parents. Many are in AAA - Syracuse, Pawtucket, Gwinnett, SWB, OKC are all owned wholly or in substantial part by their parents. In AA, the Phillies own Reading, the Braves own Mississippi, the Cardinals own Springfield, and the Astros own Corpus. Most of the FSL is owned by the MLB parents, which makes sense as they play in what also serve as the Spring Training parks. I think there are a couple more scattered in A ball (the Braves might own all their teams), but that's most of it.