DO NOT, DO NOT take US 30 east from Breezewood. It's all 2 lane, mountains and curves. There are a couple runaway truck ramps east of Breezewood.
The best way to Gettysburg from Breezewood is, stay on the PA Turnpike and take the Gettysburg/US 15 exit. Yes, you will pay tolls but, it is an easy drive.
If you were not towing, I would tell you to take 30. It's a nice drive.
But not while towing.
Depending on where you are in Maryland, it may be better to take I 70 to Hagerstown and I-81 north to Chambersburg. 30 from Chambersburg to Gettysburg Isn't bad. One mountain, no curves, mostly straight road. But there is traffic.