ok a few issues.
1) the quote problem, this must be rather simple surely?
2) instead of having "Each how many messages", why not have another system where you can choose when the ad should be repeated and how many times, so:
Display an ad every how many posts?: 4
Do this how many times?: 3
This would mean the ad shows 3 times on the first, fourth and 8th post. This is a better system i think.
aside from these two issues, it's bording on perfect. thanks!