Settings for shipping - need help

Hello.
I try to set up my first site with an online shop. I have decided to use ZenCart, but I've got stuck to the setting tax/shipping settings.
I searched this forum for other people questions/answers but in the end I decided to ask for help.
Well, is a Nutrition products shop.
Al the examples of shipping settings where for US or Canada, so maybe someone could help me out.
I intend to sell only on national area, an I have about 40 districts (zones).
The payment method will be cash on delivery.
And, of course, I use VAT tax, the same rate in all zones (actually in whole country). VAT tax I setted up. (19%).
In my city I'll deliver myself (no mail service), but in the other zones I'll use the national mail service ( based on weight of the products and distance).
For orders over 100$, we offer free delivery (only LOCO - in my city - where I can deliver personaly). The other zones deliveries are based on mail service, so the costs remains.

So. I've tried flat rate, but how can I set it only LOCO and to get it off for over 100$ orders.

I have tried some setting combinations, but faced the step1 of 3 stuck problem, and so on.

Well, what would the best setting plan for my situation?
How can I introduce the costs of my national mail service costs?