Send me a PM with your email address and I'll shoot you a very large work book filled with components and sourcing info.
1. That is still crazy overkill. You could use 1/2" square for your stand and still be over the top on strength. The brewstands people build could literally hold up their house. It looks nice, but is a bit silly as far as practicality goes.
2. You have low pressure NG.
3. I have a lot of info in the workbook. Also, searching about HBT will turn up a large number of threads that will be helpful to you.