For feed training I used the bait and switch method on the 4 lions I've had in the past. Put in a small live fish, after he eats it skip a small silver side through the water right at the lions face as fast as you can. It should trigger a auto attack before he notices its dead. Do this for the next few feedings and then just skip in a silver side. After a couple of months he will not care what it is and will be eating from your hand.
As for the tank mates I would watch for the trigger going after his side fins, cause if he nips the lion once it will go into definsive mode and one fish if not both will die. If the lion feels a threat he will go head down with his spines too the threat. So that will be a early warrning if you see the lion resonding to the 2 other fish.
Hope it works out, you will love the lion.