Without getting too much into Spoilers, Deekin is the only henchmen you can have for all three chapters. You'll also meet two more in Chapter 2 that you can bring into Chapter 3 and will meet a final one in Chapter 3.
A main trick is that you can use the Relic of the Reaper in Chapter 2 to set up a bind point at the merchant in Drearing's Deep (best prices from a mechant in the campaign) and another at the Isle of the Maker or Shaori's Fell. This will allow you to complete every area without triggering the final part of Chapter 2 (which will happen once you approach certain parts of the main city after completing 3 out of the 5 areas).
Also, some items (special ammunition to be specific) often exceed the vendor purchasing cap in a stack but splitting allows you to get more gold.
Finally, saving some of the best items to vendor for Chapter 3 helps since the merchant buy cap goes up from 10k to 50k.
Bows aren't very good except as an AA, ranged weapons just kind of suck by default in NWN.
