Please do not post the same thing multiple times. The board software automatically flags certain posts as needing moderator attention. This happens the most often for new users. I'm pretty sure this is made clear at the time you attempt to post. Posting the same thing over and over again just makes that many more posts the moderators have to weed through later. This makes us sad. Don't make us sad. If your post/thread doesn't appear, just wait a while. Don't post it again. If it hasn't shown up by the next day, then you can try again. I normally go through posts in the mornings, and try to check a few times throughout the day, but I'm not here 24/7. There will typically be a significant delay before posts are approved. Just be patient.
Yep, it is a cummulative process. The more apps you make, the more experienced you become and the more the quality of the apps increases. This leads to improved sales and a better chance of getting the occasional feature/review. You also build up a code base of reusable code which makes it quicker to develop ever more polished apps.
Of course this is offset by the added maintenance of having several apps, such as support, bug fixes, new features, screenshots and so on, which can start to eat up a fair chunk of your time.
I have achieved somewhere close to your 'comfortable' level of income over a period of two years working on apps part time, and I don't consider myself to have been particularly 'lucky'. I have never been featured on the main page by Apple and I have never had a review on one of the big review sites. It's just been a steady gain through hard work, enthusiasm (and a healthy does of obsession helps too)!