Do I need a minimum balance (existential deposit) to keep my KILT account live?

Yes, KILT account addresses have a minimum “existential deposit” of 0.01 KILT. If the amount in your account drops below that it will be deactivated (“reaped”). This works as a security feature to prevent attacks on the blockchain. The account can later be reactivated by sending more KILT Coins to it, but the reaped funds cannot be recovered.