Is it permissible for me to shorten and combine prayers, or to shorten them only, or is none of that permissible for me, knowing that I travel 60 km daily back and forth to college? And is it permissible for me to say the taslim in the third rak'ah if I join a congregational prayer with the intention of shortening it?

The minimum distance for which the shortening and combining of prayers are legislated for a traveler is four "burd" (approximately 83 kilometers), and this distance is considered for a one-way journey only. Accordingly, the shortening or combining of prayers is not legislated for the questioner because the mentioned distance is less than the considered distance. It is not permissible for him to intend to shorten the prayer, whether he prays behind an Imam or not. A traveler is required to pray in full if he prays behind a resident Imam.