Would this be an acceptable translation of Tibullus on page 279, lines 175-178?
Quis fuit horrendos primus qui protulit enses?
Quam ferus et vere ferreus ille fuit!
Tum caedes hominum generi, tum proelia nata,
tum brevior dirae mortis aperta via est!
Who was he that first brought forward the terrible swords?
How savage and truly ironlike was he!
Then the slaughter of humankind, then battles were born,
then a quicker path was opened to a horrendous death.
(I know that generi is in the dative case, but I think “slaughter of humankind” sounds better in English)
Also a related question:
I have recently re-read all of Familia Romana because I felt that I was struggling too much with the poetry in chapter XXXIV. The strange word order, omitted words, idioms and new words were overwhelming. Would you say that one should feel comfortable with those bits of poetry before moving on to Roma Aeterna? It kind of felt like they were too advanced for my current level, but maybe I should just re-read a few more times…
Perhaps it is slaughter and battles that are born and you can then take “generi hominum” as “to the race of men” or some other similar phrase.
As you have mostly only studied prose in Familia Romana it is no surprise that the poetry presents difficulties. Most of Roma Aeterna is prose I think and so you don’t need to make a study of poetry before you continue. Before tackling Roma Aeterna you should decide how much you are going to read. The intention is that you make a selection from it. If you have lots of time and the inclination there is of course nothing to stop you reading the whole thing. Whether it"s worth reading a prose version of chunks the Aeneid is something each individual would have to decide.
Reading poetry in one’s native language can be demanding so reading Latin poetry won’t be plain saying either. Re-reading is always a good idea whatever one’s level! 
dirae mortis is genitive, but as with generi, your translation works better in English. Otherwise, you have everything in good order.
You’ve identified some of the difficulties of reading Latin verse. I would suggest wrestling with them and not avoiding them, especially if reading Latin verse is one of your aims. It shouldn’t take long to develop the skill to reading Latin poetry. I think your reaction of horrified feelings of inadequacy was shared by most of us when we started reading Latin verse.
Part of the initial difficulty involves the abundant rhetorical figures, such as plural for singular and synecdoche/metonymy.
The hexameter/elegy vocabulary is somewhat different from Latin prose, in part because many prose words don’t fit the meter, and this is a reason for some of the rhetorical figures mentioned above.
One point you should notice in the excerpt from Tibullus is the placement of the adjective horrendos before the caesura modifying the noun enses at the end of the line. This, as well as other patternings of noun/adjective phrases that at first blush seems unnatural, is very common in Latin verse. At first, these patterns seem bizarre, but once you get used to them, they come to feel quite natural.
The Roman poets exploited the ability of Latin, as a highly inflected language, to support these patterns, and they are part of what makes the best Latin verse so beautifully chiseled. You need to pay attention to the meter, and in particular caesuras, to appreciate the artistry.
The constraints of the hexameter, which result in some of the difficulties you noticed, remind me of what Proust wrote about rhyme: the tyranny of rhyme forces poets to find their most beautiful verses.
Thanks to both of you for your excellent responses. You’ve given me hope that this is something that can be mastered. Tomorrow I’m moving on to chapter XXXIV, and this time I’m going to wrestle fiercely like little Hercules in his cradle. 