Sharp pain = stop.
Is your pain just from this workout, or is it a lingering problem? If the latter, you should seek out a orthopedist to look at it.
If it just happened, give things a rest, ice the knee for the first 48 hours or so, take some ibuprofen, and then see how it feels (having stopped taking the ibuprofen for at least 8-10 hours so it is not masking the pain). If the pain persists check out the orthopedist option.
On the gym, ask around you might find an alternative. If you are planning on trying to lift heavy, you need good form and proper equipment. You will need to work on the former, and unless you can find a better alternative to your gym you'll need to get creative in a smart way by doing some reading for ideas about how to use what you have to get a decent workout.
All I've heard is negatives on Smith machines, but having never had to worry about them, I haven't paid much attention. Search out Smith machine on this site & I'm sure you'll find articles and lots of forum posts.
On your deadlifts, if the pain you experienced is not a serious injury or structural problem, you'll want to learn how to do them well. This isn't an easy exercise to do correctly, as with almost every complex movement lift there is a lot to keep track of and some neuro-muscle learning that needs to happen.
I'm not really sure about using an EZ-curl bar for the exercise (others will surely chime in on this), but you may want to seek out some help. There is probably a strength coach for one or more of your schools athletic teams. See if they can point you to someone to work on your form (they may help you themselves but your less likely to get told that they can't help if you just ask if they know someone who can help).
Your gym probably won't have anyone you can trust from what it sounds like, but in asking around you might find a gym, club, or trainer. You can also read up on proper squat and dead form in articles on this site, and Mark Rippetoe's beginning strength book is a great resource on these lifts.
Having someone knowledgeable observe you is always best, because know matter how much you learn about the lifts you can't always see all the little (& not so little) things you do when you perform a lift.
Start wimpy light (like just an empty bar on squats and a bar with plates or some other way to raise it to where it would be w/ 20kg plates on for the deads), and train on getting perfect form. Each session that you perform a lift add some weight (2.5 or 5 kg.). And only progress if you can do the planned number of reps with good form (i.e., a bad form rep doesn't count).
You may feel a bit self conscious, but training your body to perform a complex exercise with good form will allow you to later lift heavier, target the muscles correctly, and minimize the risk of injury. In other words, be patient and don't try to skip ahead. The heavy weight will come soon enough, and you are trying to build a long-term habit that will produce life-long results not get to x weight in 2 months.
My final caution is watch doing too many deads in the same session you squat. Deads are tough if done right and you've already nailed many of the same muscles with squats. 1 low-rep set of deads is enough after several sets of squats. If you are doing too many of both, you are asking for an injury and will probably make slower long-term progress than by doing fewer quality reps with higher weight.
Good luck. I know what it is like to work with less than ideal equipment available, and the frustration of being a limited-income student who couldn't join a quality gym. Stick with it and keep seeking out others in your area who also lift and hopefully you will find help. You never know, you may stumble upon a new friend or two and even be invited to train in someone's well-equipped home gym.