There are still 20 more games to be played by Barcelona, so there is still a very big chance for Barcelona to enter the top 4 to be able to play
in the Champions League next season. But to be able to compete for the La Liga trophy this season is impossible for Barcelona, so indeed finishing
in the top 4 is a reasonable target for Barcelona to achieve this season.
Barcelona don't have more games than other clubs to play in La Liga. They have same total matches to play so it is not advantage for Barcelona.
In addition, if you are a strong team and can manage to win, more available matches to play mean more chances to collect more points. Oppositely, if you are a bad team, more available matches to play means more chances to lose more points and fall further behind other opponents. I believe Barcelona are facing with the second scenario.