Is it not possible to have something in the welcome message, or a room with rules that you spawn in, and can't leave until you've read all the rules?
When I'm hosting, or a friend is hosting and I'm essentially in control, I just keep an eye on all the players.
Obviously you do find people who you can trust and don't need to watch, but otherwise, keep an eye on newer players or even quiet players with the /spy command.
If you see them doing something they shouldn't, then warn them not to do it, if they continue, it's as simple as a Ban, even for just 5 minutes.
It's not rude. They were warned. If they don't have the decency to do what they're told and respect the server, then they're not wanted.
They can consider the ban as a time-out to think about what they've done.
Most people won't rejoin, and that means they didn't care about being there.
If they do rejoin, 90% of the time, they come back and behave, but if they do come back and mess around again, they get a longer ban.
I barely ever permanently ban, over than for people who do completely stupid things, like spamming over other peoples work or destroying it, and I do permanently ban the stupid people who join the server, shout swears, then leave, thinking they're too fast to be banned.
Admin Menu, Clear Bricks, BanPlayer.
Anyway, there is a lot of responsibility to hosting a server. You'd have to keep an eye on people a lot, and that can and almost defintely will mean you aren't always focussing on your own building or whatever it is you're doing.
It's a bit of a commitment, but if you're wanting a good server, it's required for someone to do it.
Trustworthy friends that can be Admins are a godsend in this sense, if they can help keep the place running smoothly.
And don't feel bad about banning people. If someone has to leave for the greater good of the server, then get rid of them.
There's no point letting them sabotage the fun that you and the others in the servers are trying to have.
Just take it easy, keep calm, get rid of those who need to, ignore the guilt and make your server a fun and enjoyable place.
Afterall, the whole reason of hosting is to have fun. There's no point doing it if you're not going to have any.