The forum rules changes are good. Perhaps, tone, you could set up a welcome email in which the rules are laid out clearly but kindheartedly? This can be auto sent to new subscribers with the title "please read carefully before posting". Just an idea :-)
Then, we can refer offeners to the rules again should that not work, as a polite but clear reminder.
I did this recently and the chap apologised and I assume will correct his behave. The system worked. It will naturally take a few weeks to see if it is going to work for the majority of people.
For better or for worse, this is the Internet. The anonymity inherent with the internet will mean some people will always be ruder here than in person. Tis just what it is.
Those of us that are kind and sharing will always get more out of this forum that those that aren't. Don't get me wrong, I am all for fairness. But I doubt there is a perfect solution. Just iteration on existing ideas :-)