The gap to the last spot for Champions League is 13 points, 12 points for the Europa League, or mathematically it is about 4-5 matches win.
With the fact that there are still 17 matches to go, mathematically Juventus is still having the chance to catch the position but ofc it is hard.
What Juventus need to do now is to try to win all the remaining 17 matches and hoping for the other team above their current position losing many points.
It is not impossible to happen but really hard to happen unless there will be miracles for them.
Juventus have the opportunity to get ticket to UEL even though they failed to reach 4th place in the final standings this season. they must win the Coppa Italia. However, they should be able to beat Inter Milan in the Semi-Finals. This is the best chance for Juventus to go to UEL, if they fail in this match, it will be even more difficult for them to play at UEL next season because it wil depend on their final standing positions.
If everything goes aright for Juventus your calculation is true, but if this also becomes reality Juventus is totally screwed:
"Juventus may face 20-point deduction for undeclared wage payments"
Now for everyone who thinks this is old news, this is actually on top of the deduction they recently received and is currently under investigation. It is sad because it shows that Juventus hasn't learnt a lot from the scandal back at the time when they were relegated into Serie B in 2006 or so.