First I think 2500 lb TC for fulltiming is not going to be comfortable.
You definitely need tie-downs.
Right now there is not much choice than Torklift front tie downs. Cost about $400.
Rear tie-downs can be easy manufacture what will save you $300 TL cost.
Till you buy the camper - you don't know how much modifications your truck will need. You might need to upgrade wheels as well.
Factory bed mat is good.
Air bags or helper springs, or timbrens - it is all personal choice.
I had good experience with air. Others like steel or rubber.