Testing my neo6 (same as your ebay link at the top), until I get at least in the high 30's to near 40 db the unit will NOT lock and provide a position fix, even after many many minutes. This inside not near a window.
Once it gets a position fix and has initial lock it is happy to keep working even at low 30's. If the signal on a lot of sats drops to 30 to 20 then it loses fix easily until the signal becomes stronger.
So, until you get your signal strength up, I doubt you'll get an initial fix. From your pictures above, your signal strength is too low to get an initial fix and too low to maintain it reliably.
The neo8 in the same position on my desk does much better, but then it has a slightly larger passive antenna and has a more sensitive receiver and of course since it also catches the glonass constellation it is likely to get stronger signal through the roof of our house by just having more sats 'sneaking' signal between rafters and stuff in the attic...
cheers,
george.