Take that last photo to a locksmith to be sure, but my money's on a Kwikset-compatible keyway
The last photo you provide (head-on shot of the outside, with the keyway clearly visible) tells me that whoever actually made the lock is probably irrelevant -- the keyway strongly resembles one of the de facto standard Kwikset keyways that are used on low-end door locks across the USA. (It can't be a Schlage due to the "squared" shape of the upper warding piece, and it can't be a Yale either because of the lack of a "tail" at the top of the keyway. The warding is also not nearly paracentric (across the middle of the keyway) enough to be found on a higher-end lock -- even Schlages are a fair bit this way, never mind an Abus or some other European make.)
Of course, IANAL (I am not a locksmith), so if you want to be sure, take that last photo and your keys to your friendly local locksmith and they'll be able to tell you far more confidently than I can what you've got. They almost certainly will be able to rekey a Kwikset-compatible lock as well, as they're compatible with most "generic" lock pins out there.