That's not a great CH trip. I used to commute between Pgh and Alexandria weekly. If it were morning, I actually made a stop at the McD's on the Nat'l Highway just past the MD border (that was faster at the time due to constant PA Tpk construction). Never found anything before/after or in Breezewood.
If it were nearing lunch, I found that I could deal with the food court in that outlet complex right off the highway in Hagerstown. I found it better than the average mall food court (maybe because I was always really hungry by that time). But that doesn't mean it was great by any means.
Frederick Md has some interesting options in the old downtown section. there is a good brewpub. last time we were driving through we stumbled on to a mostly, but not strictly vegetarian restaurant, perhaps Orchard??? but then you're only an hour from DC by time you're there!!!
you know, i used to pass through breezewood frequently thinking "there's got to be something here..." but i never did find it.
i dunno what time you'll be heading thru frederick (or if that's too close to home, anyway) but on roadtrips as tradition we used to hit the mountain view diner (i think that's what it was called?) leaving town in the early hours.
i think i've been to that same brewpub! we've hit that a couple times before a play at the MET... couldn't tell you its name to save my life though.