Regarding FIP, the Wall is presumably beneficial for O's pitchers fielding independent type stats.
In theory, yes. FIP is calculated based on actual HR rates, which Orioles pitchers at home should benefit from with fewer homers out to LF. xFIP actually calculates home runs based on how many you'd expect to allow if you had a normal HR/FB rate. So if you give up more homers per flyball than average, that'll drive up your ERA and FIP but your xFIP would give you a homerun penalty only for the league average rate of your flyballs allowed and not the exact number that became actual home runs.
In Gibson's specific case, his HR/FB rate is only a tiny bit worse than league average, so his FIP and xFIP are nearly identical. If you break it into home/road, he's had a higher HR/FB at home than on the road which feels unlucky and is reflected in his xFIP being a little lower than his FIP at home, but a little higher on the road. Both FIP and xFIP, home and away, are still much better than his ERA. Order of about 1 run. Part of that is just Gibson, though. For his career he's always had a worse ERA than his FIP (0.31 runs worse) and xFIP (0.48 runs worse) by what feels like a meaningful amount.