About daily deposit maximum, they can't create SWAP.HIVE. So if there is a lot of demand for SWAP.HIVE deposits and not much for HIVE withdraws, entire SWAP.HIVE supply is used and new deposits will be refunded until someone withdraws their HIVE and SWAP.HIVE is available again.
You can check liquidity here: @leodex/wallet

Hive-Engine "official" deposit method can create their own SWAP.HIVE for every deposit.