The first impression I get of you my friend is that you for the most part KNOW what to do, but get frustrated in the seeming lack of progress in the actual execution of it. You know that tension is bad. You know you need to play to a metronome, you know that you need to have a smaller picking motion, but there are a lot of things that still elude you in the working out of those things. This is the exact reason that even I as a guitar teacher myself have a guitar teacher, because there is always a hidden dimension of things we do not know that through road blocks in front of practically doing what we do know. Even Beethoven (musical genius extraodinaire) had a music teacher and a piano teacher for a good portion of his career! So if you need it, do not feel "cheapened" by getting a teacher, it will only add wisdom to you (and results). By the look of the girl playing in the video (doing awesome, very rare find a female rocking out like that!) she probably has or had a teacher, which would explain the prodigious progress in a relatively small amount of time. I know you said that you are not into asking for help, which shows that you are a "can do" kind of person, which is good, but last time I checked, no one knows everything and it is more often that which we don't know what hinders our progress.

Sorry for the block-o-text, but just focus on attempting to apply one of the musical principles at a time such as: remaining tension free, or timing, etc. You can alternate practicing the different aspects of your playing, but you must focus on one at a time in order to see progress.

www.jamesericksonmusic.com