I am glad you are not giving up. My first handful of times practicing with the system took me forever and I was exhausted and tired just getting set up. I had to hang there for a bit to get the energy to climb back down. I promise it gets a lot better! As far as the Jim Stepp knot goes, I had that happen to me early on as well. During the second twist, I captured the Rope instead of just the standoff. This makes it act like an actual knot and makes it tight. Watch the video that they have on the Wild Edge website very closely and you will see what I am talking about. If done correctly, it will not tighten up on you like what you experienced.
The main difference that I have noticed between the Run and Gun setup versus a preset tree stand like I was used to is the amount of time needed. I used to walk up to a tree, tie my bow to the lift line and climb the preset "ladder". It took a grand total of one or two minutes to climb the tree, get in the stand and lift my bow. Starting off, I would give myself 1 hour to select a tree, get prepped at the base, climb and tie in, then lift bow and be ready to hunt. It now takes me about 15 minutes during daylight and 20 to 25 minutes in the dark. I tend to go much slower and try to be much quieter in the early morning hours when you can hear a pin drop. Do not be afraid to take a break halfway up to cool down and not rush! Keep up the hard work!