1. quem sīc Pallas petit ante precātus

Your Identification: 

Pallas, praying beforehand, attacks him in this way
with a prayer having been made beforehand, Pallas attacks him in this way
Pallas, who has prayed beforehand, attacks him in this way

2. perterrita agmina

Your Identification: 

the terrified lines
the terrifying lines
the lines having terrified

3. et sociī cessērunt aequore iussō

Your Identification: 

and the allies withdrew from the ordered plain
and the allies, having ordered it, withdrew from the plain

4. haud alia est Turnī venientis imāgō

Your Identification: 

no different was the appearance of Turnus who had arrived
no different was the appearance of Turnus as he was coming on
no different was the appearance of Turnus who was about to arrive

5. Turnus ovat spoliō gaudetque potītus

Your Identification: 

Turnus delights and rejoices in the spoil, as he gains possession of it
Turnus delights and rejoices in the spoil that has been obtained
Turnus delights and rejoices in the spoil, having gained possession of it

6. ō dolor atque decus magnum reditūre parentī!

Your Identification: 

O [source of] grief and great glory returned to his parent!
O [source of] grief and great glory returning to his parent!
O [source of] grief and great glory that will return to his parent!