I think it's more a privacy issue, like CoinBase could start blocking PD withdrawals etc. Although I assume the "hot wallet" is actually just a collection of addresses that change all the time.
There is also no reason for a public cold wallet since there are no public investors risking money at PD (unlike those other sites that you mentioned.)
As as I know it's a WALLET that holds all deposit addresses, all addresses then payout withdrawals. Wallets topped up when needed to be.
That's usually how it works (at least that's how it works on BitDice I think?)
Not really, The deposits address are not really called a hot wallet, it is just a deposit address from the players, in moneypot, the withdrawal are scrambled by paying from others deposits, if the deposit addrress was sort of low of funds needed to pay a withdrawal, then a hot wallet will send it using a mixer, this is how I believe it works, dont know if it is the same with PD