The daily 5-7mi will not get it warm.
The weekly 30mi will resolve that issue.
The trailer is light, and you would probably be better off with the 6.4 (coming from a person that has a 5.9 CTD to pull a 6-7k trailer).
Why Aisin? Save the money and get the 68 (the stock auto trans). My dad has a '14 pulling ~15k with the 68RFE, works great. I'm impressed and jealous of how nice it is. If you daily pulled, or the truck was strictly a trailer puller then you could maybe justify the Aisin, but not at your weight or towing frequency.
