so what kind of coinage do you need to properly stake (yes i've read up but there are some contradiction, eg my client says 1000, but a tutoral says 10000 etc etc etc)?
any advantage in more coinage?
prior to staking any advantage or need in keeping the client running?
it is 10000, the client has a typo
more coinage is related to your importance on the network, and therefore increases your odds of harvesting a block, but not directly, check out the white paper for more detail
Harvesting involves block creation, so something needs to be running. It can be your local computer running a node, your own remote node on a vps, or on a public node.
Soon, (i hope) there will be a system of rewards for those running their own nodes. So that will be another way of profiting in addition to harvesting
is there any advantage in keeping the client open prior to having your coins mature to staking age?