Starting out with 2iu and going from there, is a good idea. At first I would keep the carbs on the high side to be safe, but after you work your way up and get used to it you shouldn't need 500 grams of simple carbs or whatver 15g/iu every 45 min works out to. You can use less and still get good anabolic effect without getting fat or causing your body to release a ton more insulin and raise your chances of insulin resistance.
You also shouldn't need all simple carbs, your insulin is already spiked right? You just spiked it with a needle. Just make sure they don't take too long to digest or it won't keep up with the fast insulin.
It's impossible to say if 8iu is "enough". You just have to experiment and see. You could probably even work up to 20-30 3-4 times a week for 28 days or so. You might as well hit it hard and then get out and take some time off right? As far as taking it first thing in the morning, that works too, but post workout should be better. Both works well. You can also take pre-workout and that might be best for your schedule, but don't do that untill you know exactly what you are doing and how you will react.
I've done that in conjuntion with pwo shots and didn't see much boost during the workout so I didn't try it more than a couple of times but I've heard good things as far as gains from pre-workout only.
I've tried working up to 10iu morning and pwo on training day, 10iu on first off day and then off second off day,then training day starts over again with 2xd. I did this for two weeks and then did two weeks 10iu morning and 10iu post workout/afternoon every day for two weeks. Nothing else at that time and I gained about 10 pounds in that month. My stomach was kind of getting bloated and blurry so I stopped at a month.
I kept about 7 pounds and I think what I lost was sq water because my midsection tightened up quick after I went off, with no diet changes. That was with Humulin-R Somewhat recently I did a Humalog and Test Susp cycle. I did 30iu on training day, 10 morning, 10 pwo, 10 4 hours later, 10iu on first day off, and none second day off, then start over again with training day(training every third day). The TNE was 700mg/wk. I did this for 25 days. Again I gained about ten pounds but I would have expected more.
I guess there is a diminishing response. Maybe I was getting resistant, but fasting glucose was always around 100. Lately I just use 10iu pwo and maybe the next day so 10iu 4-5 days a week. I really don't know if it's doing much anymore so I might go off for awhile and take an OGTT(Oral Glucose Tolerance Test). Or try taking Avandia.
I don't think shutting down your own production is a big risk, I think the biggest danger(besides dying or going into a coma a few hours after injecting) is long term insulin resistance from long term use. Not much research or documented experience exists for healthy people using exogenous insulin. I think you could get pretty good results though from using it for a month and then taking at least a month off before going on again and there shouldn't be much danger.
I recomend taking fasting blood suger levels before you start and several times during the cycle and an OGTT before and after to see how your body reacted. Hope this helps, Good Luck!(Sorry for the Long-Ass post)