I am sorry you are having so many complications. They tried to install a PICC for me last September but the veins in my left arm were too small even for a pediatric line, and after 7 failed attempts at the one vein in my right arm that looked almost big enough they found that it was scarred and unusable from a blood clot during my colectomy. So I now have a portacath instead.
I am not sure why everyone is saying you can't gain weight on TPN; I was able to discontinue TPN just a couple weeks ago because I had put on 28 pounds in seven months and I am now at a healthy weight.
I hope things start going better for you soon!