I would suggest keeping the car. You might not need it for work, but are you going to do all of your video productions in that same building? That could get boring fast. Also, what happens when you get an opportunity for a much better job, but it's 10 miles from the nearest bus route? So even if the current car is too expensive to keep and maintain, maybe consider a $1000 beater for emergencies.
Then I would consider a lighting kit. Lights are already basically commodities, so your investment isn't likely to become obsolete next week, and it will add a lot to the quality of your productions. I watched probably 30 minutes of that video you posted and saw a lot of creativity, but it still just looked like any home video in many ways. Creative lighting will help you get much more out of the equipment you already have.
You say you're a musician, so I'll assume you already have some decent audio equipment. Figure out how to make the most of it for your movies.
I wouldn't want to disappoint Mom, but you should also just keep the computer. My computer is slower than yours and it works fine for most things, even HDV editing. Rendering can be slow at times, but it also made me learn some useful tricks that I might not have learned if I had a great computer. More RAM might be a consideration.
And lastly, give yourself a price, maybe $2,000, and buy the best camera you can get when you save up the goal amount. Don't worry about it becoming obsolete. Worrying about that will just either keep you from ever buying anything (there will always be something better next year), or you will always be depressed looking at how much you could have saved by waiting 6 months. Just buy it and use it. The $2-4,000 stuff today is already freak'n amazing. By the time you save up $2,000 you might be able to get an HVX200. Of course there will be something for $4,000 that blows it away, but oh well.
In summary:
Buy a decent lighting kit. Keep the car. Keep the computer. Keep the camcorder. Keep working. Keep filming. Save up for a better camcorder. Then save up for a better computer.
The idea is to spring first for the things that hold their value the longest or might get more expensive over time.
Just my opinion.