I was an interpreter for years however, after a car accident I can't do it any more. I get a headache when I watch sign language. I did watch your video and you did a very good job.
I'm full of a lot of praise, have one bit of advice and some sign suggestions that should help the next time you come across the words.
PRAISE Great choice of dress. it was dark and your hands stood out beautifully. I thought your face was fine. Yes, you didn't have alot of expression going on, you also didn't call too much attention to yourself. It is best to use less than too much. Deaf people don't want to watch you act - they just want to know what's going on. Your hands are what interests them. That is why it is important to chose the right clothing - you don't want to wear or do anything that would detract. OR bring attention to you or away from the singer, teacher or speaker. Remember you are JUST the interpreter - not the entertainment - and you did that beautifully!!!
ADVICE- and I give this because it was given to me when I was first starting out. Although you were pretty fluid, sometimes you would bounce with the beat or repeat signs to the beat. "Don't stutter." I was told to try to not do that because it can be tiring on the deaf person's eyes. The example they used when explaining it to me was to liken it to stuttering - how it can be tiring for hearing people to listen to a bad stutterer. Not to mention, hard on your hands. After you've been interpreting for a while and carpal tunnel has started to set in, you won't want to move those hands any more than you need to.
SIGN SUGGESTIONS You asked if you used the signs correctly and I did notice some that I would have done differently...
Breath - Rather than brushing up your chest, think of how you breathe. Your chest rises and falls. So using the same hand position, with your right hand above the left, lay them on your chest and then
breathe lifting both hands away and towards your chest a few times.
Together - joined as one. Do you know the sign for "of"? Both hands in 'f' shape with the thumbs interlacing? A good way to sign "together" is to bring those hands together, thumbs interlacing, symbolizing two people coming together. Once they are together do a forward circle with your hands.
World - Fingers in 'w' position, Rather than side ways the world rotates forward.
Walk - watch which way you are walking. You have the hands shaped fine but the video looked like you were moving backwards rather than forwards.
Darkness - Same as Walk - correct shaped hands, wrong direction. Darkness descends on us - not opens up.
Good luck.
By the way, starting pay for a certified interpreter at the local university is $45,000 (more than the people who teach them how to do it earns!!!).