is KB3REN's TVFool plot. Judging from plotting KDKA's signal coverage before making the radar plot, you are in the area where western PA's rolling hills have scattered shadows all over the place from the downtown Pittsburgh transmitters. That someone across town can get better results is no surprise - that's how signal coverage can vary in this kind of terrain that that's why a tool like TVFool can be so handy.
Now, to the details! WNPB 33 (24.1) comes in like a ton of bricks. No surprise, as you have a clear shot (LOS = line of sight) at that antenna from Chestnut Ridge. Just about anything will pick this up. Next down the list is WTAE 51 (4.1) and that is because it is 15 miles closer to you than any other Pittsburgh station. Following is a repeater for WPXI on 23, WDTV 5 (5.1), and KDKA 25 (2.1). After KDKA, signal strengths take a real hit, and I doubt seriously that you have any chance to get any of these weaker stations indoors. Frankly, you're going to have a challenge getting anything beyond WNPB.
The indoor antenna that I've seen recommended more than any other is the Terk HDTVi. You could try this if you haven't already, but I can't guarantee that you'll get anything but WNPB and, maybe, WTAE. For reliable reception, the digital TV signal must be stronger than background noise by a certain amount. TVFool helps you gauge this with the "NM", or noise margin, values.
Signals with an NM of 0 will decode, given no other losses. Since signals are subject to fading not accounted for in the predictions, an NM of 10 is usually considered the right goal. In your case, your building probably knocks 20 dB or so off signals, so we need to subtract that from NM's in your report. That puts everything but WNPB below 0. Antenna gain will add to the NM, but indoor antennas typically have only 1 to 3 dB gain (amplifiers DO NOT count in these calculations). That's why you're having such trouble.
If you can tolerate a bigger antenna inside, you can build a 4-bay bow-tie antenna pretty easily for almost nothing. Check out plans here
that evolved from the "coat hangar" designs from YouTube and other sites. Use the plans from this site only, as the "coat hangar" designs are far from optimum. You could get as much as 14 dB gain, which would get you enough signal to maybe pull in KDKA most of the time.
Without being able to move the antenna outside, that's about the best you can do. Good luck!