What you say is true and it's also where HIVE is shining. One wallet with a simple address (your username) and not a gibberish string of words. I get the confusion about staking though. Many of the blockchains and projects doesn't make it at all easy.
Yes, I think there's a timer of 5 minutes between every crosspost you can do but as far as I know there's no limit to the number of times you can do it.