In terms of side effects, even at the lower dosages you're taking (compared to what I was taking with it) you'll probably notice what I can only describe as a kind of manic sedation. There is also the histamine reaction from codeine, which might cause you to get itchier or get dried out more easier than with hydrocodone.
But with the dose you're at, I doubt the side effects will be problematic. If sedation isn't a huge issue and the histamine reaction is, take 25-50mg of diphenhydramine with your dose. If sedation is an issue, use one of the newer non-drowsy antihistamines.
Everyone is different, so YMMV with this, but I'd guess that taking up to 150mg/day for two weeks won't result in any significant withdrawal symptoms. Especially if you're using it medicinally and non-recreationally (opioids used for this purpose seem to rarely lead to dependency developing so quickly).