@coolpinkone, I know you're getting bombarded with a lot of suggestions, but...  My first suggestion is to only concentrate on trying to do one thing at a time.  If you try to do to much, you may just become frustrated.  Suggestions have been:

1. Don't be tense

2. Employ dynamics by varying your bow speed and pressure

3. Learn to use vibrato

4. Don't play long notes on open strings

and so forth.

I think it's too much to try to do that all at once.  I would suggest taking one thing at a time, starting from the easiest, either 1) dynamics or 2) don't use the open strings and tackle just that.  Once you think you've got that engrained, only then tackle the next thing. Of course, you can try to relax more while you're doing it, which is, I guess, 2 things.

For dynamics, just watch Pierre's video on dynamics and use the bowing techniques etudes in the etudes section of the "sheet music" tab up at the top.  There's a ton of good stuff in there.

Or, if you want to tackle not using open strings -- that's easy enough.  Just play the song in a different key so that there are no notes on open strings, such as Eb.  Here's a link to the song in Eb.

You're showing big improvement in tone and intonation. Just keep listening to the pros do it and play along with their recordings and try to blend in. That will allow you to hear, learn and understand  the little nuances of what they do to add character and feeling to this piece, or any piece for that matter. There is a lot more to it than just adding vibrato, such as changes in volume, sliding into certain notes, small variations in the actual duration of notes as opposed to what's written in the score and how they accent notes, to name just a few. It has been said that reading is like thinking with the brain of someone else. If that is true, then music is like feeling with someone else's heart.