Stu gave you really good advice. Just to add a few comments:
Check out this video on the deadlift:
http://video.google.com/videoplay?docid ... 2460&hl=en
You need to get that bar over the middle of your foot, and when you go down to the bar and grab it, your shins should be in contact. You should be dragging the bar up your legs. You don't need to now, because the weight is so light, but once you get more plates, you'll find the bar wants to drag up your legs. So train that now.
Bench Press - push the bar straight up. You get a little of a curve. The Mark Rippetoe cue I like is to pick a spot on the ceiling where the bar goes when you push it straight up, and keep your eyes there. Look at it the whole set, and just push the bar up to that spot. It's a good way to ensure you don't push it up-and-back. That doesn't help you any.
Otherwise, what Stu said. Especially the part about getting some more plates. Try Craigslist, I've heard they have "Play It Again Sports" or something like that now, check garage sale listings. Buy cheap, it's just weight. If you have to, make your own. But get the bar heavier. The weight you're doing now is moving pretty fast, that says to me you can move a lot more soon!