Ah, that is an error. Previously, reclaimers could get an extra weapon relic, but I decided it was more fluffy for power armor and also made BoS style warband possible. So the table is incorrect. As for your second question, you are correct that only arbiters get access to the Gatling laser. So yes, you would burn through your relic choices, though your leader still gets his free allocation for a relic. Also, you can get a third relic after a few games and I will say the next book will have a warband progression so that as you get more experience you get access to more relics and elite choices. If you simply can't wait, I would definitely let you take the model and just ignore the relic cap, as long as your opponents can do the same. Happy gaming.
Joey