I like to arrange covers based on live versions performed by the original artist. It is a REALLY helpful tool.
That said, here's my really quick notes based on a cursory view:
You put yourself out there and did it. Kudos. It takes courage to play in front of an audience, and to then post video on an internet forum asking for critiques...well, that speaks for itself.
As to what I would offer up? Vocals were pitchy and not powerful enough. Your singers need to project more, and focus on singing from their diaphragms. A powerful singing voice doesn't come from the mouth or throat, it comes from the chest-generally the deeper the better. Also, it seemed like they were a little unclear on their respective parts and ended up doubling each other when harmonies would have been more appropriate.
Dynamics are everything in a live performance. Every note and rhythm can be spot on, but if the song is played at a constant volume level from beginning to end it will end up sounding flat (not in terms of pitch, but emotion). The audience won't know exactly what is missing, but they will notice it. Generally, in a pop song the verses should be quieter and the choruses should come up in volume. Not over the top contrast, but enough to differentiate them from each other, yet subtle. When you do this right you will see a kind of swell in your audience right before the choruses because they anticipate what's coming and they want to sing along, dance, whatever. But dynamics isn't just about overall volume. There also needs to be some dynamic interplay between the performers. When the band drops out for the first verse in the beginning, right before the line "You'd better take it from me," your drummer keeps playing at the same volume. Since everyone else has dropped out at that moment, I would have him play markedly softer to provide some contrast and free your singers up to emote a little more. Also, he sounds like he's having difficulty keeping time through his fills. Whenever I have encountered this with my own drummers, the solution is to always simplify the fill in order to emphasize and keep good time. He can work on solidifying more complicated fills in practice and bring them to rehearsal, but his primary role as a drummer is to, over and above everything, to keep solid time.
Take a look at this and see if you see what I am talking about regarding dynamics, vocal projection and harmonies.
I hope this helps and you're able to put it to use. Keep at it! Record everything you do and always critique. No one gets better by focusing on what they did right. The only way to improve is to find weaknesses and improve upon them.
