1. Hire a good lawyer and get good advice. The best defense is a good offense and all that.
Make sure he has no ability to use company funds. Cancel his company debit / credit card if he received one as a director of sales. Send an official letter by registered post letting him know that he does not have the ability to authorize expenses above $100 or so.
Then follow your lawyer's advice on firing him from the sales position.
Make sure your lawyer communicates the non-compete part with him properly - so that he realizes that if he leaves now, he won't be able to profit from the idea at all - and its better to stay with you and earn 22% of the pie than go for 100% and get a big fight on his hands that he will most likely lose.
2. > The person had a large rolodex in a segment of our market.
This tells us that the person's reputation can be adversely affected. Threat of bad press could maybe get him in line.
Also, it would be a good idea to find at least one or two common connections and try making them mediators.
3. This is the stick. You need to offer him a carrot too.
Make him an offer: he does not work with you. He retains his shares and plays a role as an investor. He gives up the board seat - and remains a silent investor. He gives you a connection / letter of referral for all the contacts he is sitting on - for a flat fee. No vesting of shares.
Position this "getting a fee for writing a letter of introduction to his connections" - as the carrot. A lot depends on how you phrase it.
4. Start contacting other investors who could maybe buy this person's share out. I doubt if you can find and close someone in 7 days, but the sooner you start looking, the better.
Under no circumstances should you make threats like this without talking to a lawyer.
Now go get a lawyer.
Put NOTHING of a threatening nature in any form of writing or voicemail. Hell, write nothing that doesn't document that you are in the right for that matter. Consider everything you do as possible evidence in a future court hearing and act accordingly.
Good luck & don't lose hope.
 2001: A Space Odyssey