I would suggest the longest motor that fits, for power and cooler temps. A lower kv around 1500 is ideal for 6S use. I would run the stock ESC for as long as it lasts. I would service all 3 diffs and make sure they're shimmed properly and full of oil. The center diff oil needs to be a lot thicker, I would start with 100k. I would suggest a real set of tools. MIP makes a nice 1.5, 2.0, 2.5mm hex driver wrench set for a good price.