I have a similar situation with channels 11 and 13 (not the Baltimore ones, though) that may be of some assistance to you. My channels 11 and 13 are 65 miles away, and are at 6.7 and 4.6 dB NM, respectively. Your TVFool report shows your channels 11 and 13 at 6.3 and 4.3 dB NM, respectively, very similar to mine. My tv requires a signal strength of 35 or better on my tv's signal meter in order to reliably lock a signal.
I have a Winegard YA-1713 VHF-high antenna in my attic, which is a very good VHF-high antenna (9-10 dB gain). In the attic, I can only occasionally lock channels 11 and 13 late at night (meaning that the signal only creeps over 35 at that time). I recently temporarily tested my YA-1713 outside at chimney height (maybe 20 feet above ground level) and channels 11 and 13 locked in fine at a 64 signal strength for both stations. At least in my area, I would roughly estimate that the YA-1713 would reliably receive VHF-high stations (channels 7-13) up to about 50 miles from inside my attic and maybe 75-85 miles outside at chimney height.
Your RCA ANT751 isn't going to provide that much gain, so if it is getting your Baltimore channels 11 and 13 marginally from inside your attic, perhaps a YA-1713 would get them just fine from your attic. If you pointed a YA-1713 either directly toward Baltimore, or maybe in-between the Baltimore and Washington directions (for 7 and 9), maybe that would work just fine for you. You do lose maybe 25-35% of your signal from the attic, but that can be compensated for somewhat by bigger antenna(s).
Can you still return your RCA ANT751 (maybe you're still within 30 days of purchase)? The YA-1713 isn't too expensive, and you would join it with a suitable not-too-expensive UHF-only antenna with a UVSJ to get a much better overall solution, perhaps from your attic. Maybe this combination would be a better (and not-too-expensive) solution:http://www.solidsignal.com/pview.asp...-(YA1713)&c=TV
Of course, these are much bigger antennas, so your attic would have to be able to handle the size. I have mine hung separately 10 feet apart from each other along the very highest point of my attic (just about touching the rafters) on 4-foot pieces of 1" PVC pipe ($2), each attached to a rafter by a single long screw going through a drilled hole an inch from the end of each pipe. In the spring, I'll have to add an outside antenna for my distant stations, but maybe yours will come in from the attic.
Hope this is helpful...