That's the idea, but if you really can't hold the derailleur in the proper position it might really be bent. Did anything hit it? I'd swear that cage looks slightly bent. Loosen the bolt and move the cage so it's roughly parallel w/ the chainrings, then tighten the bolt back up. If it wants to settle 'tail out' then adjust it a little 'tail in' so when you tighten it down it stays parallel. Make sure you undo the cable so it doesn't pull the derailleur down on the mount. Then start all over w/ your limit screws.
1) position derailleur correctly
2) shift rear to large cog
3) adjust low limit in front to @ 1.0mm
4) shift rear to small cog
5) attach front cable
6) pedal crank and slowly pull on the cable (by hand, under down tube) til the chain shifts onto the large ring
7) adjust high limit to @ 1.0mm
8) adjust cable tension if needed
test repeatedly to make sure everything is good...crank arm doesn't hit cage, chain doesn't drop or throw...