Longer version of my answer
I know you had to get to work so I gave you a quick answer and you can read this later:
1. You have to start him, as soon as possible. 350 is not a crazy number at all, but it *is* over the renal threshold, and sustained numbers that are untreated can lead to ketones. You can read all about those in the wiki about feline diabetes. You'll see a ton of stuff that's important and you will retain approximately 5% of it LOL Don't worry, this is a huge learning experience for everyone so don't feel like you have to remember everything right away. Most important is you get him under treatment to both prevent further, and also to heal the current, damage that occurs to the body while diabetic.
2. 1/2u.. In my opinion, which should not be confused with a medical opinion, Webber is not running high enough to warrant a very large dose in the beginning. You can always raise this dose, but for now, just get him under treatment. You'll need around a week at a dose to see if it's working. You will need to exercise patience that you never knew you had. You will rail and scream and whine and moan and worry. His numbers might even go higher than they were when he was NOT on insulin. It's normal, just stay your course.
3. Read read read. As I said above, this information is so hard to remember, but it's so necessary for you to know what you're doing for his health. Read the health links from the forum index, read the stickies, read other people's condos.. and then go back and read it all again. If someone says something you don't understand, ask them. They'll all be happy to explain, and no one at all will think you're stupid for asking. You should see some of the questions I asked LOL
Have a terrific day at work and I can't wait to see how Webber does this week
..C
