Need better geosearch, not sure if I miss something

I need a good range search for my website. My community is country based and limited to germany. Nothing worldwide necessary.

So I want that people register and put their city and zip code. But there are some difficulties. When they register with the map, they can put city only or even country only. On this way it is not possible to find them with their zip code when searching it with the range search.

When I put there city and zip code only at the registration, it is not possible to find someone if he puts city and zip by hand without using the auto-completion.

What is this 'region' option? Can I improve the search with that option? Are there any addons that make this search really usable?

Please, I need any advice, because range search is absolutely necessary for me. I need anything that works reliable.

Additionally I found out, that though the search within EasySocial uses Google Maps information, it does not work everytime. I found several zip codes, that can be found on Google Maps but not inside the registration area of EasySocial.

I think it would be even better and more reliable to let people enter the zip code only and make a dropdown menu for the country. Viewable in their profile should be the first 2 or 3 numbers of their zipcode. But in the database should be the complete one so the range search could check with entering if the zip code exists and make a realiable result when searching the distance.

Is this possible and did I just miss how to realize this?

Just to show an example, you can see what I mean here: http://www.finya.de/Registration?

You can choose between Deutschland and Österreich and then you just put your zip code. The system then takes the city, but I think that is not necessary. For a reliable distance and range serach, the zip code is just fine, because the system tells you, when there is a wrong and not available zip codes taken.