How many Salvage droid levels are there

I also get a bux reward when opening a cargo container for cargo that I've already received. I have not noticed your pattern of increasing bux rewards - my rewards have varied from 2 - 10 bux; but it could be that since I have several bitizens and 2 levels unlocked that the reward varies depending on what you see again?

One pattern I can confirm: When I unlock a bitizen, I first get the typical find bitizen quest to grant them access - this will give you 1 buck back; and then I will immediately get a new cargo delivery that gives me a 5 bux reward for having already received this cargo. This means that you get a refund of 6 bux on the off-chance that you actually manage to unlock a new bitizen.

Panna city med was from the Christmas event, so I don't think they'll make that available again. From what I can tell, if you see a planet (Kashyyyk, endor, etc...) and you click on it, you'll get a graphic showing what you might be able to get. For instance, Kashyyyk shows two characters and a level. However, you have to purposefully search on that particular planet/area to possibly get that reward. Rescan (every 12 hours, or on demand for 5 bux) rearranges your scanning options. You get one free scan on the first area once a day or on demand for 5 bux; but I have not seen a planet on that scanning level. Essentially what that means is that you can't get these rewards without using bux. Which sux.