We'd absolutely take him to the vet first, to check for chip and health.
We saw him on Saturday afternoon (Feb. 4), outside same home we first saw him at (west side of 76th street, closer to 34th ave.). That would lead us to believe he lives there, or at least is fed or finds shelter there. He still looked well-fed, but was a bit dirtier this time. He was bumping/rubbing/crawling under the car in the driveway, though, which was covered with winter grime, so that could explain it. But he had more of that grungy street cat look.
He let us pet him, although not as much as the first time we saw him - at that point he was very friendly and trusting, and even followed us up AND down the block, several times between 34th and 35th. He basically hung out with us, walking with us and stopping when we did, for almost a half hour... This time he stayed at the driveway and then walked away from us and disappeared behind the car after a minute or two.
We walked past a few times on Sunday and did not see him. I really hope he was curled up somewhere, safe and warm indoors.